Cartridge including tape-shaped magnetic recording medium

ABSTRACT

A cartridge is provided and includes tape-shaped magnetic recording medium; and cartridge memory; wherein cartridge memory includes communication unit that communicates with recording/reproducing device in state where cartridge is loaded on recording/reproducing device; storage unit; and control unit that stores, reads, and transmits information, wherein information includes manufacturing information of cartridge and adjustment information for adjusting a tension applied to the tape-shaped magnetic recording medium in a longitudinal direction of tape-shaped magnetic recording medium thereof, tape-shaped magnetic recording medium has a plurality of servo bands, and wherein a temperature expansion coefficient α of the tape-shaped magnetic recording medium satisfies 6 ppm/° C.≤α≤8 ppm/° C.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/460,542, filed on Aug. 30, 2021, which application is acontinuation of U.S. patent application Ser. No. 16/886,191, filed onMay 28, 2020, issued as U.S. Pat. No. 11,107,505 on Aug. 31, 2021, whichapplication is a continuation of U.S. patent application Ser. No.16/453,403, filed on Jun. 26, 2019, issued as U.S. Pat. No. 10,796,724on Oct. 6, 2020, which claims priority to Japanese Patent Application JP2019-073161 filed on Apr. 5, 2019, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a cartridge and a cartridge memory.

BACKGROUND ART

In recent years, in a magnetic tape (tape-shaped magnetic recordingmedium) used as a data storage for a computer, a track width and adistance between adjacent tracks are very narrow in order to improve adata recording density. When the track width and the distance betweentracks are narrow in this way, a maximum allowable change amount as adimensional change amount of the tape itself due to an environmentalfactor such as changes in temperature and humidity is smaller.

For this reason, PTL 1 proposes a magnetic tape medium capable ofsuppressing a dimensional change in a width direction caused by anenvironmental factor to a low level and securing stablerecording/reproducing characteristics with less off-track. Furthermore,PTL 1 describes that the dimensional change amount in the widthdirection with respect to a tension change in a longitudinal directionis reduced.

CITATION LIST Patent Literature

[PTL 1]

JP 2005-332510 A

SUMMARY Technical Problem

In recent years, due to a demand for increasing the capacity of amagnetic tape, the number of recording tracks has increased, and thewidth of a recording track has been narrowed. For this reason, afterdata is recorded on a magnetic tape, if the width of the magnetic tapefluctuates even slightly due to some causes, it may be impossible for arecording/reproducing device to accurately reproduce the data recordedon the magnetic tape, and an error may occur. In other words,reliability of reproduction may be decreased.

In the present disclosure, it is desirable to provide a cartridge and acartridge memory capable of suppressing a decrease in reliability ofreproduction.

Solution to Problem

According to an embodiment of the present disclosure, a first disclosureprovides a cartridge including:

a tape-shaped magnetic recording medium;

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in whichthe information includes adjustment information for adjusting a tensionapplied to the magnetic recording medium in a longitudinal directionthereof,the magnetic recording medium has an average thickness t_(T) satisfyingt_(T)≤5.5 [μm], and the magnetic recording medium has a dimensionalchange amount Δw satisfying 650 [ppm/N]≤Δw in a width direction thereofwith respect to a tension change of the magnetic recording medium in thelongitudinal direction thereof.

A second disclosure provides a cartridge including:

a tape-shaped magnetic recording medium; and

a storage unit having an area in which adjustment information foradjusting a tension applied to the magnetic recording medium in alongitudinal direction thereof is written, in which the magneticrecording medium has an average thickness t_(T) satisfying t_(T)≤5.5[μm], and the magnetic recording medium has a dimensional change amountΔw satisfying 650 [ppm/N]≤Δw in a width direction thereof with respectto a tension change of the magnetic recording medium in the longitudinaldirection thereof.

A third disclosure provides a cartridge memory used for a tape-shapedmagnetic recording medium, including:

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in which the information includes adjustmentinformation for adjusting a tension applied to the magnetic recordingmedium in a longitudinal direction thereof.

A fourth disclosure provides a cartridge memory used for a tape-shapedmagnetic recording medium, including

a storage unit having an area in which adjustment information foradjusting a tension applied to the magnetic recording medium in alongitudinal direction thereof is written.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of a configurationof a recording/reproducing system according to a first embodiment of thepresent disclosure;

FIG. 2 is an exploded perspective view illustrating an example of aconfiguration of a cartridge;

FIG. 3 is a block diagram illustrating an example of a configuration ofa cartridge memory;

FIG. 4 is a cross-sectional view illustrating an example of aconfiguration of a magnetic tape;

FIG. 5A is a schematic view of a layout of a data band and a servo band;FIG. 5B is an enlarged view of the data band;

FIG. 6 is a perspective view illustrating a configuration of a measuringdevice;

FIG. 7 is a flowchart for explaining an example of operation of arecording/reproducing device at the time of data recording;

FIG. 8 is a flowchart for explaining an example of operation arecording/reproducing device at the time of data reproduction;

FIG. 9 is a schematic diagram illustrating an example of a configurationof a recording/reproducing system according to a second embodiment ofthe present disclosure;

FIG. 10 is a flowchart for explaining an example of operation of arecording/reproducing device at the time of data recording; and

FIG. 11 is a flowchart for explaining an example of operation of arecording/reproducing device at the time of data reproduction.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in the followingorder. Note that in all the drawings of the following embodiments, thesame or corresponding parts are denoted by the same reference numerals.

1 First embodiment

2 Second embodiment

3. Modification

1. First Embodiment

[Outline]

The present inventors are studying a magnetic tape suitable for use in arecording/reproducing device capable of keeping the width of themagnetic tape constant or almost constant by adjusting a tension appliedto the magnetic tape in a longitudinal direction thereof.

Furthermore, it is conceivable that the adjustment of the tension isperformed using tension adjustment information stored in advance in acartridge memory. However, according to findings of the presentinventors, as described above, since a general magnetic tape has a smalldimensional change amount in a width direction with respect to a tensionchange in a longitudinal direction, it is difficult to keep the width ofthe magnetic tape constant or almost constant by therecording/reproducing device.

Therefore, the present inventors have intensively studied a magnetictape capable of keeping the width of the magnetic tape constant oralmost constant by the recording/reproducing device. As a result,contrary to the above-described general magnetic tape, a magnetic tapehaving a large dimensional change amount in a width direction withrespect to a tension change in a longitudinal direction, specifically, amagnetic tape in which a dimensional change amount Δw in a widthdirection with respect to a tension change in a longitudinal directionsatisfies 650 [ppm/N]≤Δw has been found.

[Configuration of Recording/reproducing System]

FIG. 1 is a schematic diagram illustrating an example of a configurationof a recording/reproducing system 100 according to a first embodiment ofthe present disclosure.

The recording/reproducing system 100 is a magnetic taperecording/reproducing system, and includes a cartridge 10 and arecording/reproducing device 50 capable of loading and unloading thecartridge 10.

[Configuration of Cartridge]

FIG. 2 is an exploded perspective view illustrating an example of aconfiguration of the cartridge 10. The cartridge 10 is a magnetic tapecartridge conforming to a linear tape-open (LTO) standard, and includes:in a cartridge case 12 including a lower shell 12A and an upper shell12B, a reel 13 around which a magnetic tape (tape-shaped magneticrecording medium) MT is wound; a reel lock 14 for locking rotation ofthe reel 13; a reel spring 15; a spider 16 for releasing a locked stateof the reel 13; a slide door 17 that opens and closes a tape outlet 12Cformed in the cartridge case 12 so as to straddle the lower shell 12Aand the upper shell 12B; a door spring 18 that urges the slide door 17to a closed position of the tape outlet 12C; a write protect 19 forpreventing erroneous erasure; and a cartridge memory 11. The reel 13 hasa substantially disk shape with an opening at the center, and incudes areel hub 13A and a flange 13B made of a hard material such as plastic. Aleader pin 22 is disposed at one end of the magnetic tape MT.

The cartridge memory 11 is disposed near one corner of the cartridge 10.The cartridge memory 11 faces a reader/writer 57 of therecording/reproducing device 50 in a state where the cartridge 10 isloaded on the recording/reproducing device 50. The cartridge memory 11communicates with the recording/reproducing device 50, specifically,with the reader/writer 57 according to a wireless communication standardconforming to an LTO standard.

[Configuration of Cartridge Memory]

FIG. 3 is a block diagram illustrating an example of a configuration ofthe cartridge memory 11. The cartridge memory 11 includes: an antennacoil (communication unit) 31 that communicates with the reader/writer 57according to a prescribed communication standard; a rectification/powersupply circuit 32 that generates power using an induced electromotiveforce from a radio wave received by the antenna coil 31 and performsrectification to generate a power supply; a clock circuit 33 thatgenerates a clock using an induced electromotive force similarly fromthe radio wave received by the antenna coil 31; a detection/modulationcircuit 34 that performs detection of the radio wave received by theantenna coil 31 and modulation of a signal transmitted by the antennacoil 31; a controller (control unit) 35 including a logic circuit or thelike for determining a command and data from a digital signal extractedfrom the detection/modulation circuit 34 and processing the command anddata; and a memory (storage unit) 36 that stores information.Furthermore, the cartridge memory 11 includes a capacitor 37 connectedin parallel to the antenna coil 31, and the antenna coil 31 and thecapacitor 37 constitute a resonant circuit.

The memory 36 stores information and the like related to the cartridge10. The memory 36 is a non-volatile memory (NVM). The memory 36preferably has a storage capacity of about 32 KB or more. For example,in a case where the cartridge 10 conforms to an LTO-9 standard or anLTO-10 standard, the memory 36 has a storage capacity of about 32 KB.

The memory 36 has a first storage area 36A and a second storage area36B. The first storage area 36A corresponds to a storage area of acartridge memory conforming to an LTO standard prior to LTO 8(hereinafter referred to as “conventional cartridge memory”) and is anarea for storing information conforming to an LTO standard prior to LTO8. The information conforming to an LTO standard prior to LTO 8 is, forexample, manufacturing information (for example, a unique number of thecartridge 10) or a usage history (for example, the number of times oftape withdrawal (thread count)).

The second storage area 36B corresponds to an extended storage area fora storage area of the conventional cartridge memory. The second storagearea 36B is an area for storing additional information. Here, theadditional information means information related to the cartridge 10,not prescribed by an LTO standard prior to LTO 8. Examples of theadditional information include tension adjustment information,management ledger data, Index information, and thumbnail information ofa moving image stored in a magnetic tape MT, but are not limited to thedata. The tension adjustment information includes a distance betweenadjacent servo bands (a distance between servo patterns recorded inadjacent servo bands) at the time of data recording on the magnetic tapeMT. The distance between the adjacent servo bands is an example ofwidth-related information related to the width of the magnetic tape MT.Details of the distance between the servo bands will be described later.In the following description, information stored in the first storagearea 36A may be referred to as “first information”, and informationstored in the second storage area 36B may be referred to as “secondinformation”.

The memory 36 may have a plurality of banks. In this case, some of theplurality of banks may constitute the first storage area 36A, and theremaining banks may constitute the second storage area 36B.Specifically, for example, in a case where the cartridge 10 conforms toan LTO-9 standard or an LTO-10 standard, the memory 36 may have twobanks each having a storage capacity of about 16 KB. One of the twobanks may constitute the first storage area 36A, and the other bank mayconstitute the second storage area 36B.

The antenna coil 31 induces an induced voltage by electromagneticinduction. The controller 35 communicates with the recording/reproducingdevice 50 according to a prescribed communication standard through theantenna coil 31. Specifically, for example, mutual authentication,transmission and reception of commands, and exchange of data areperformed. The controller 35 stores information received from therecording/reproducing device 50 through the antenna coil 31 in thememory 36. The controller 35 reads out information from the memory 36 inresponse to a request from the recording/reproducing device 50, andtransmits the information to the recording/reproducing device 50 throughthe antenna coil 31.

[Configuration of Magnetic Tape]

FIG. 4 is a cross-sectional view illustrating an example of aconfiguration of a magnetic tape MT used for the cartridge 10. Themagnetic tape MT is, for example, a perpendicular magnetic recordingtype magnetic tape, and includes: a long substrate 41; a base layer(nonmagnetic layer) 42 disposed on one main surface of the substrate 41;a recording layer (magnetic layer) 43 disposed on the base layer 42; anda back layer 44 disposed on the other main surface of the substrate 41.Note that the base layer 42 and the back layer 44 are disposed asnecessary and may be omitted. Hereinafter, of both main surfaces of themagnetic tape MT, a surface on which the recording layer 43 is disposedmay be referred to as a magnetic surface, and the surface oppositethereto, on which the back layer 44 is disposed, may be referred to as aback surface.

The magnetic tape MT has a long shape and travels in a longitudinaldirection thereof during recording/reproduction. Furthermore, themagnetic tape MT can record a signal at the shortest recordingwavelength of preferably 100 nm or less, more preferably 75 nm or less,still more preferably 60 nm or less, particularly preferably 50 nm orless, and is used, for example, for a recording/reproducing devicehaving the shortest recording wavelength within the above range. Thisrecording/reproducing device may include a ring type head as a recordinghead.

(Substrate)

The substrate 41 serving as a support is a flexible, long, andnonmagnetic substrate. The substrate 41 is a film, and an averagethickness T_(sub) of the substrate 41 is preferably 3 μm or more and 8μm or less, more preferably 3 μm or more and 4.2 μm or less, still morepreferably 3 μm or more and 3.8 μm or less, and particularly preferably3 μm or more and 3.4 μm or less. The average thickness T_(sub) of thesubstrate 41 is determined as follows. First, a magnetic tape MT havinga width of ½ inches is prepared and cut into a length of 250 mm tomanufacture a sample. Subsequently, layers of the sample other than thesubstrate 41 (that is, the base layer 42, the recording layer 43, andthe back layer 44) are removed with a solvent such as methyl ethylketone (MEK) or dilute hydrochloric acid. Next, the thickness of thesample (substrate 41) is measured at five or more points using a laserhologage manufactured by Mitutoyo Corporation as a measuring device, andthe measured values are simply averaged (arithmetically averaged) tocalculate the average thickness T_(sub) of the substrate 41. Note thatthe measurement points are randomly selected from the sample.

The substrate 41 contains, for example, at least one of a polyester, apolyolefin, a cellulose derivative, a vinyl-based resin, an aromaticpolyether ketone (PAEK), and another polymer resin. In a case where thesubstrate 41 contains two or more of the above materials, the two ormore materials may be mixed, copolymerized, or laminated.

The polyester includes, for example, at least one of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polybutyleneterephthalate (PBT), polybutylene naphthalate (PBN),polycyclohexylenedimethylene terephthalate (PCT),polyethylene-p-oxybenzoate (PEB), and polyethylenebisphenoxycarboxylate.

The polyolefin includes, for example, at least one of polyethylene (PE)and polypropylene (PP). The cellulose derivative includes, for example,at least one of cellulose diacetate, cellulose triacetate, celluloseacetate butyrate (CAB), and cellulose acetate propionate (CAP). Thevinyl-based resin includes, for example, at least one of polyvinylchloride (PVC) and polyvinylidene chloride (PVDC). The aromaticpolyether ketone (PAEK) includes, for example, polyether ether ketone(PEEK).

The other polymer resin includes, for example, at least one of polyamideor nylon (PA), aromatic polyamide or aramid (aromatic PA), polyimide(PI), aromatic polyimide (aromatic PI), polyamide imide (PAI), aromaticpolyamide imide (aromatic PAI), polybenzoxazole (PBO) such as ZYLON(registered trademark), polyether, polyether ketone (PEK), polyetherester, polyether sulfone (PES), polyether imide (PEI), polysulfone(PSF), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate(PAR), and polyurethane (PU).

(Recording Layer)

The recording layer 43 is a so-called perpendicular recording layer, andcontains, for example, magnetic powder and a binder. The recording layer43 may further contain one or more additives selected from the groupconsisting of a lubricant, conductive particles, an abrasive, a rustinhibitor, and the like, as necessary.

The recording layer 43 has a surface having a large number of holesformed thereon, and a lubricant is preferably stored in the large numberof holes. This makes it possible to reduce a friction due to a contactbetween the magnetic tape MT and a head. The large number of holespreferably extend in a direction perpendicular to the surface of therecording layer 43. This is because a property of supplying thelubricant to the surface of the recording layer 43 can be improved. Notethat some of the large number of holes may extend in the perpendiculardirection.

An average thickness t_(m) of the recording layer 43 satisfiespreferably 35 [nm]≤t_(m)≤90 [nm], more preferably 35 [nm]≤t_(m)≤80 [nm],still more preferably 35 [nm]≤t_(m)≤70 [nm], particularly preferably 35[nm]≤t_(m)≤50 [nm]. When the average thickness t_(m) of the recordinglayer 43 satisfies 35 [nm]≤t_(m), output can be secured in a case wherean MR type head is used as a reproducing head, and thereforeelectromagnetic conversion characteristics can be improved. Meanwhile,when the average thickness t_(m) of the recording layer 43 satisfiest_(m)≤90 [nm], an influence of a demagnetizing field can be reduced in acase where a ring type head is used as a recording head, and thereforeelectromagnetic conversion characteristics can be improved. The averagethickness t_(m) of the recording layer 43 can be determined as follows.First, the magnetic tape MT is thinly processed perpendicularly to amain surface thereof to manufacture a sample piece. A cross section ofthe sample piece is observed with a transmission electron microscope(TEM) under the following conditions.

Device: TEM (H9000NAR manufactured by Hitachi, Ltd.)

Acceleration voltage: 300 kV

Magnification: 100,000 times

Next, using the obtained TEM image, the thickness of the recording layer43 is measured at 10 or more points in a longitudinal direction of themagnetic tape MT. Thereafter, the measured values are simply averaged(arithmetically averaged), and the obtained value is taken as theaverage thickness t_(m) (nm) of the layer 43.

As illustrated in FIG. 5A, the recording layer 43 preferably has aplurality of servo bands SB and a plurality of data bands DB in advance.The plurality of servo bands SB is disposed at regular intervals in awidth direction of the magnetic tape MT. A data band DB is disposedbetween adjacent servo bands SB. In each of the servo bands SB, a servosignal for performing tracking control of a magnetic head is written inadvance. In each of the data bands DB, user data is recorded by therecording/reproducing device 50.

An upper limit value of a ratio R_(S) (=(S_(SB)/S)×100) of a total areaS_(SB) of the servo bands SB with respect to an area S of a surface ofthe recording layer 43 is preferably 4.0% or less, more preferably 3.0%or less, and still more preferably 2.0% or less from a viewpoint ofsecuring a high recording capacity. Meanwhile, a lower limit value ofthe ratio R_(S) of the total area S_(SB) of the servo bands SB withrespect to the area S of a surface of the recording layer 43 ispreferably 0.8% or more from a viewpoint of securing five or more servotracks.

The ratio R_(S) of the total area S_(SB) of the servo bands SB withrespect to the area S of a surface of the recording layer 43 isdetermined as follows. First, a surface of the recording layer 43 isobserved using a magnetic force microscope (MFM) to acquire an MFMimage. Subsequently, using the acquired MFM image, a servo bandwidthW_(SB) and the number of servo bands SB are measured. Next, the ratioR_(S) is determined from the following formula.Ratio R _(S)[%]=(((servo bandwidth W _(SB))×(number of servobands))/(width of magnetic tape MT))×100

A lower limit value of the number of servo bands SB is preferably 5 ormore, more preferably 5+4n (in which n represents a positive integer) ormore, and still more preferably 9+4n or more. When the number of servobands SB is 5 or more, an influence on a servo signal due to adimensional change of the magnetic tape MT in a width direction thereofcan be suppressed, and stable recording/reproducing characteristics withless off-track can be secured. An upper limit value of the number ofservo bands SB is not particularly limited, but is for example, 33 orless. The number of servo bands SB can be confirmed as follows. First, asurface of the recording layer 43 is observed using a magnetic forcemicroscope (MFM) to acquire an MFM image. Next, the number of servobands SB is counted using the MFM image.

An upper limit value of a servo bandwidth W_(SB) is preferably 95 μm orless, more preferably 60 μm or less, and still more preferably 30 μm orless from a viewpoint of securing a high recording capacity. A lowerlimit value of a servo bandwidth W_(SB) is preferably 10 μm or more. Itis difficult to manufacture a recording head capable of reading a servosignal having a servo bandwidth W_(SB) of less than 10 μm.

A servo bandwidth W_(SB) can be determined as follows. First, a surfaceof the recording layer 43 is observed using a magnetic force microscope(MFM) to acquire an MFM image. Next, a servo bandwidth W_(SB) ismeasured using the MFM image.

As illustrated in FIG. 5B, the recording layer 43 can form a pluralityof data tracks Tk in a data band DB. The total number of data tracks Tkthat can be formed in the recording layer 43 is preferably 6000 or morefrom a viewpoint of securing a high recording capacity. An upper limitvalue of a data track width W is preferably 3.0 μm or less, morepreferably 1.6 μm or less, still more preferably 0.95 μm or less, andparticularly preferably 0.51 μm from a viewpoint of improving a trackrecording density and securing a high recording capacity. A lower limitvalue of the data track width W is preferably 0.02 μm or more inconsideration of a magnetic particle size.

The recording layer 43 can record data such that a minimum value L of adistance between magnetization inversions and the data track width Wsatisfy preferably W/L≤200, more preferably W/L≤60, still morepreferably W/L≤45, particularly preferably W/L≤30. When the minimumvalue L of the distance between magnetization inversions is a constantvalue, and the minimum value L of the distance between magnetizationinversions and the track width W satisfy W/L>200 (that is, the trackwidth W is large), a track recording density is not increased.

Therefore, it may be impossible to sufficiently secure a recordingcapacity. Furthermore, when the track width W is a constant value, andthe minimum value L of the distance between magnetization inversions andthe track width W satisfy W/L>200 (that is, the minimum value L of thedistance between magnetization inversions is small), a bit length isshort, and a linear recording density is high. However, SNR may besignificantly deteriorated due to an effect of spacing loss. Therefore,in order to suppress the deterioration of SNR while securing therecording capacity, W/L is preferably in a range of W/L≤60 as describedabove. However, W/L is not limited to the above range, and may satisfyW/L≤23 or W/L≤13. A lower limit value of W/L is not particularlylimited, but for example, satisfies 1≤W/L.

The recording layer 43 can record data such that the minimum value L ofthe distance between magnetization inversions is preferably 50 nm orless, more preferably 48 nm or less, still more preferably 44 nm orless, and particularly preferably 40 nm from a viewpoint of securing ahigh recording capacity. A lower limit value of the minimum value L ofthe distance between magnetization inversions is preferably 20 nm ormore in consideration of a magnetic particle size.

(Magnetic Powder)

The magnetic powder contains powder of nanoparticles containing ε ironoxide (hereinafter referred to as “ε iron oxide particles”). The ε ironoxide particles are hard magnetic particles that can obtain a highcoercive force even when being fine particles. ε iron oxide contained inthe ε iron oxide particles is preferably crystal-oriented preferentiallyin a thickness direction (perpendicular direction) of the magnetic tapeMT.

The ε iron oxide particle has a spherical shape or a substantiallyspherical shape, or has a cubic shape or a substantially cubic shape.Since the ε iron oxide particle has the shape as described above, in acase where the ε iron oxide particles are used as magnetic particles, acontact area between the particles in a thickness direction of themagnetic tape MT can be reduced, and aggregation of the particles can besuppressed as compared to a case where hexagonal plate-shaped bariumferrite particles are used as the magnetic particles. Therefore,dispersibility of the magnetic powder can be enhanced, and a bettersignal-to-noise ratio (SNR) can be obtained. The ε iron oxide particlehas a core-shell type structure. Specifically, the ε iron oxide particlehas a core portion and a two-layered shell portion disposed around thecore portion. The two-layered shell portion includes a first shellportion disposed on the core portion and a second shell portion disposedon the first shell portion.

The core portion contains ε iron oxide. ε iron oxide contained in thecore portion preferably contains an ε-Fe₂O₃ crystal as a main phase, andmore preferably contains ε-Fe₂O₃ as a single phase.

The first shell portion covers at least a part of the periphery of thecore portion. Specifically, the first shell portion may partially coverthe periphery of the core portion or may cover the entire periphery ofthe core portion. The first shell portion preferably covers the entiresurface of the core portion from a viewpoint of making exchange couplingbetween the core portion and the first shell portion sufficient andimproving magnetic characteristics.

The first shell portion is a so-called soft magnetic layer, andincludes, for example, a soft magnetic material such as α-Fe, a Ni—Fealloy, or a Fe—Si—Al alloy. α-Fe may be obtained by reducing ε ironoxide contained in the core portion.

The second shell portion is an oxide film as an antioxidant layer. Thesecond shell portion contains α iron oxide, aluminum oxide, or siliconoxide. α-iron oxide contains, for example, at least one iron oxide ofFe₃O₄, Fe₂O₃, and FeO. In a case where the first shell portion containsα-Fe (soft magnetic material), α-iron oxide may be obtained by oxidizingα-Fe contained in the first shell portion.

By inclusion of the first shell portion in the ε iron oxide particle asdescribed above, a coercive force Hc of the entire ε iron oxideparticles (core-shell particles) can be adjusted to a coercive force Hcsuitable for recording while a coercive force Hc of the core portionalone is maintained at a large value in order to secure thermalstability. Furthermore, by inclusion of the second shell portion in theε iron oxide particle as described above, it is possible to suppressdeterioration of the characteristics of the ε iron oxide particles dueto generation of a rust or the like on surfaces of the particles byexposure of the ε iron oxide particles to the air during a step ofmanufacturing the magnetic tape MT and before the step. Therefore,characteristic deterioration of the magnetic tape MT can be suppressed.

The magnetic powder has an average particle size (average maximumparticle size) of, for example, 22.5 nm or less. The average particlesize (average maximum particle size) of the magnetic powder ispreferably 22 nm or less, more preferably 8 nm or more and 22 nm orless, still more preferably 12 nm or more and 22 nm or less,particularly preferably 12 nm or more and 15 nm or less, and mostpreferably 12 nm or more and 14 nm or less. In the magnetic tape MT, anarea having a half size of a recording wavelength is an actualmagnetization area. Therefore, by setting the average particle size ofthe magnetic powder to a half or less of the shortest recordingwavelength, it is possible to obtain good electromagnetic conversioncharacteristics (for example, SNR). Therefore, when the average particlesize of the magnetic powder is 22 nm or less, in a magnetic tape MThaving a high recording density (for example, a magnetic tape MT thatcan record a signal at the shortest recording wavelength of 44 nm orless), good electromagnetic conversion characteristics (for example,SNR) can be obtained. Meanwhile, when the average particle size of themagnetic powder is 8 nm or more, dispersibility of the magnetic powderis further improved, and better electromagnetic conversioncharacteristics (for example, SNR) can be obtained.

The magnetic powder has an average aspect ratio of preferably 1.0 ormore and 3.0 or less, more preferably 1.0 or more and 2.5 or less, stillmore preferably 1.0 or more and 2.1 or less, particularly preferably 1.0or more and 1.8 or less. When the average aspect ratio of the magneticpowder is within a range of 1.0 or more and 3.0 or less, aggregation ofparticles of the magnetic powder can be suppressed. Furthermore, whenthe magnetic powder is perpendicularly oriented in a step of forming therecording layer 43, resistance applied to the magnetic powder can besuppressed. Therefore, perpendicular orientation of the magnetic powdercan be improved.

The average particle size and the average aspect ratio of the magneticpowder can be determined as follows. First, a magnetic tape MT to bemeasured is processed by a focused ion beam (FIB) method or the like tomanufacture a thin piece, and a cross section of the thin piece isobserved with TEM. Next, 50 ε iron oxide particles are randomly selectedfrom the photographed TEM photograph, and a long axis length DL and ashort axis length DS of each of the ε iron oxide particles are measured.Here, the long axis length DL means the largest distance among distancesbetween two parallel lines drawn from all angles so as to come intocontact with an outline of an ε iron oxide particle (so-called maximumFeret diameter). Meanwhile, the short axis length DS means the largestlength among the lengths of an ε iron oxide particle in a directionorthogonal to the long axis of the ε iron oxide particle.

Subsequently, the long axis lengths DL of the measured 50 ε iron oxideparticles are simply averaged (arithmetically averaged) to determine anaverage long axis length DLave. The average long axis length DLavedetermined in this manner is taken as an average particle size of themagnetic powder. Furthermore, the short axis lengths DS of the measured50 ε iron oxide particles are simply averaged (arithmetically averaged)to determine an average short axis length DSave. Then, an average aspectratio (DLave/DSave) of the ε iron oxide particles is determined from theaverage long axis length DLave and the average short axis length DSave.The magnetic powder has an average particle volume of preferably 5600nm³ or less, more preferably 250 nm³ or more and 5600 nm³ or less, stillmore preferably 900 nm³ or more and 5600 nm³ or less, particularlypreferably 900 nm³ or more and 1800 nm³ or less, most preferably 900 nm³or more and 1500 nm³ or less. In general, noise of the magnetic tape MTis inversely proportional to a square root of the number of particles(that is, proportional to a square root of a particle volume).Therefore, by reducing the particle volume, good electromagneticconversion characteristics (for example, SNR) can be obtained.Therefore, when the average particle volume of the magnetic powder is5600 nm³ or less, good electromagnetic conversion characteristics (forexample, SNR) can be obtained with a similar effect to that in a casewhere the average particle size of the magnetic powder is 22 nm or less.Meanwhile, when the average particle volume of the magnetic powder is250 nm³ or more, a similar effect to that in a case where the averageparticle size of the magnetic powder is 8 nm or more can be obtained. Ina case where the ε iron oxide particle has a spherical shape or asubstantially spherical shape, the average particle volume of themagnetic powder is determined as follows. First, an average long axislength DLave is determined in a similar manner to the above-describedmethod for calculating the average particle size of the magnetic powder.Next, an average particle volume V of the magnetic powder is determinedby the following formula.V=(π/6)×DLave³

In a case where the ε iron oxide particle has a cubic shape or asubstantially cubic shape, the average particle volume of the magneticpowder is determined as follows. First, a magnetic tape MT to bemeasured is processed by an FIB method or the like to manufacture a thinpiece, and a cross section of the thin piece is observed with TEM.Subsequently, 50 ε iron oxide particles each having a plane parallel tothe TEM cross section are randomly selected from the photographed TEMphotograph, and the length L of one side of each of the ε iron oxideparticles is measured. Next, the lengths L of one sides of the measured50 ε iron oxide particles are simply averaged (arithmetically averaged)to determine an average side length Lave.V=Lave³(Binder)

As the binder, a resin having a structure in which a crosslinkingreaction is imparted to a polyurethane-based resin, a vinylchloride-based resin, or the like is preferable. However, the binder isnot limited to these resins, and other resins may be blendedappropriately according to physical properties and the like required fora magnetic tape MT. Usually, a resin to be blended is not particularlylimited as long as being generally used in an application type magnetictape MT.

Examples of the resin to be blended include polyvinyl chloride,polyvinyl acetate, a vinyl chloride-vinyl acetate copolymer, a vinylchloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrilecopolymer, an acrylate-acrylonitrile copolymer, an acrylate-vinylchloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrilecopolymer, an acrylate-acrylonitrile copolymer, an acrylate-vinylidenechloride copolymer, a methacrylate-vinylidene chloride copolymer, amethacrylate-vinyl chloride copolymer, a methacryate-ethylene copolymer,polyvinyl fluoride, a vinylidene chloride-acrylonitrile copolymer, anacrylonitrile-butadiene copolymer, a polyamide resin, polyvinyl butyral,a cellulose derivative (cellulose acetate butyrate, cellulose diacetate,cellulose triacetate, cellulose propionate, and nitrocellulose), astyrene-butadiene copolymer, a polyester resin, an amino resin, and asynthetic rubber.

Furthermore, examples of a thermosetting resin or a reactive resininclude a phenol resin, an epoxy resin, a urea resin, a melamine resin,an alkyd resin, a silicone resin, a polyamine resin, and a ureaformaldehyde resin.

Furthermore, in order to improve dispersibility of the magnetic powder,a polar functional group such as —SO₃M, —OSO₃M, —COOM, or P═O(OM)₂ maybe introduced into each of the above-described binders. Here, in theformulae, M represents a hydrogen atom or an alkali metal such aslithium, potassium, or sodium.

Moreover, examples of the polar functional group include a side chaintype group having a terminal group of —NR1R2 or —NR1R2R3⁺X⁻, and a mainchain type group of >NR1R2⁺X⁻. Here, in the formulae, R1, R2, and R3each represent a hydrogen atom or a hydrocarbon group, and X⁻ representsan ion of a halogen element such as fluorine, chlorine, bromine, oriodine, or an inorganic or organic ion. Furthermore, examples of thepolar functional group include —OH, —SH, —CN, and an epoxy group.

(Additive)

As nonmagnetic reinforcing particles, the recording layer 43 may furthercontain aluminum oxide (α, β, or γ alumina), chromium oxide, siliconoxide, diamond, garnet, emery, boron nitride, titanium carbide, siliconcarbide, titanium carbide, titanium oxide (rutile type or anatase typetitanium oxide), and the like.

(Base Layer)

The base layer 42 is a so-called nonmagnetic layer, and contains, forexample, nonmagnetic powder and a binder. The base layer 42 may furthercontain one or more additives selected from the group consisting ofconductive particles, a lubricant, a curing agent, a rust inhibitor, andthe like, as necessary.

An average thickness t_(u) of the base layer 42 is preferably 0.6 μm ormore and 2.0 μm or less, and more preferably 0.8 μm or more and 1.4 μmor less. Note that the average thickness t_(u) of the base layer 42 isdetermined in a similar manner to the average thickness t_(m) of therecording layer 43. However, a magnification of a TEM image isappropriately adjusted according to the thickness of the base layer 42.

(Nonmagnetic Powder)

The nonmagnetic powder may be made of an inorganic substance or anorganic substance. Furthermore, the nonmagnetic powder may be made ofcarbon black or the like. Examples of the inorganic substance include ametal, a metal oxide, a metal carbonate, a metal sulfate, a metalnitride, a metal carbide, and a metal sulfide. Examples of the shape ofthe nonmagnetic powder include various shapes such as an acicular shape,a spherical shape, a cubic shape, and a plate shape, but are not limitedthereto.

(Binder)

The binder is similar to that of the above-described recording layer 43.

(Back Layer)

The back layer 44 contains a binder and nonmagnetic powder. The backlayer 44 may contain various additives such as a lubricant, a curingagent, and an antistatic agent, as necessary. The binder and thenonmagnetic powder are similar to those of the above-described baselayer 42. The inorganic particles have an average particle size ofpreferably 10 nm or more and 150 nm or less, more preferably 15 nm ormore and 110 nm or less. The average particle size of the inorganicparticles can be determined in a similar to an average particle size Dof the above-described magnetic powder.

An average thickness t_(b) of the back layer 44 preferably satisfiest_(b)≤0.6 [μm]. By setting the average thickness t_(b) of the back layer44 within the above range, even in a case where the average thicknesst_(T) of the magnetic tape MT satisfies t_(T)≤5.5 [μm], the thicknessesof the base layer 42 and the substrate 41 can be kept large. This makesit possible to maintain traveling stability of the magnetic tape MT inthe recording/reproducing device.

The average thickness t_(b) of the back layer 44 is determined asfollows. First, a magnetic tape MT having a width of ½ inches isprepared and cut into a length of 250 mm to manufacture a sample. Next,the thickness of the sample is measured at five or more different pointsusing a laser hologage manufactured by Mitutoyo Corporation as ameasuring device, and the measured values are simply averaged(arithmetically averaged) to calculate the average thickness t_(T) [μm].Subsequently, the back layer 44 of the sample is removed with a solventsuch as methyl ethyl ketone (MEK) or dilute hydrochloric acid.Thereafter, the thickness of the sample is measured at five or moredifferent points again using the above-described laser hologage, and themeasured values are simply averaged (arithmetically averaged) tocalculate an average thickness t_(B) [μm]. Thereafter, the averagethickness t_(b) (μm) of the back layer 44 is determined by the followingformula.t _(b)[μm]=t _(T)[μm]−t _(B)[μm](Average Thickness t_(T) of Magnetic Tape)

The average thickness t_(T) of the magnetic tape MT satisfies t_(T)≤5.5μm, preferably t_(T)≤5.2 μm, more preferably t_(T)≤5.0 μm, still morepreferably t_(T)≤4.6 μm, particularly preferably t_(T)≤4.4 [μm]. Whenthe average thickness t_(T) of the magnetic tape MT satisfies t_(T)≤5.5[μm], a recording capacity that can be recorded in one data cartridgecan be increased compared to related art. A lower limit value of theaverage thickness t_(T) of the magnetic tape MT is not particularlylimited, but satisfies, for example, 3.5 μm≤t_(T).

The average thickness t_(T) of the magnetic tape MT is determined in asimilar manner to the average thickness t_(T) at the average thicknesst_(b) of the back layer 44.

(Dimensional Change Amount Δw)

A dimensional change amount Δw [ppm/N] of the magnetic tape MT in awidth direction thereof with respect to a tension change of the magnetictape MT in a longitudinal direction thereof satisfies 650 ppm/N≤Δw,preferably 670 ppm/N≤Δw, more preferably 680 ppm/N≤Δw, still morepreferably 700 ppm/N≤Δw, particularly preferably 750 ppm/N≤Δw, mostpreferably 800 ppm/N≤Δw. When the dimensional change amount Δw satisfiesΔw≤650 ppm/N, in adjustment of a tension applied to the magnetic tape MTin a longitudinal direction thereof by the recording/reproducing device50, it may be difficult to suppress a change in the width of themagnetic tape MT. An upper limit value of the dimensional change amountΔw is not particularly limited, but may satisfy, for example, Δw≤1700000ppm/N, preferably Δw≤20000 ppm/N, more preferably Δw≤8000 ppm/N, stillmore preferably Δw≤5000 ppm/N, Δw≤4000 ppm/N, Δw≤3000 ppm/N, or Δw≤2000ppm/N.

The dimensional change amount Δw can be set to a desired value byselecting the substrate 41. For example, the dimensional change amountΔw can be set to a desired value by selecting at least one of thethickness of the substrate 41 and a material of the substrate 41.Furthermore, the dimensional change amount Δw may be set to a desiredvalue, for example, by adjusting stretching strength of the substrate 41in a width direction thereof and a longitudinal direction thereof. Forexample, by stretching the substrate 41 more strongly in the widthdirection thereof, the dimensional change amount Δw decreases more.Conversely, by stretching the substrate 41 more strongly in thelongitudinal direction thereof, the dimensional change amount Δwincreases.

The dimensional change amount Δw is determined as follows. First, amagnetic tape MT having a width of ½ inches is prepared and cut into alength of 250 mm to manufacture a sample 10S. Next, a load is applied tothe sample 10S in a longitudinal direction thereof in the order of 0.2N, 0.6 N, and 1.0 N, and the width of the sample 10S at each load of 0.2N, 0.6 N, and 1.0 N is measured. Subsequently, the dimensional changeamount Δw is determined by the following formula. Note that themeasurement in a case of applying a load of 0.6 N is performed in orderto confirm whether abnormality has occurred in the measurement (inparticular, in order to confirm that these three measurement results arelinear). The measurement results are not used in the following formula.

$\begin{matrix}{{\Delta{w\lbrack {{ppm}/N} \rbrack}} = {\frac{{{D( {0.2N} )}\lbrack{mm}\rbrack} - {{D( {1.N} )}\lbrack{mm}\rbrack}}{{D( {0.2N} )}\lbrack{mm}\rbrack} \times \frac{1,000,000}{( {1.\lbrack N\rbrack} ) - ( {0.2\lbrack N\rbrack} )}}} & \lbrack {{Math}.1} \rbrack\end{matrix}$(In which, D (0.2 N) and D (1.0 N) indicate the widths of the sample 10Swhen loads of 0.2 N and 1.0 N are applied to the sample 10S in alongitudinal direction thereof, respectively). The width of the sample10S when each load is applied is measured as follows. First, a measuringdevice incorporating a digital dimension measuring instrument LS-7000manufactured by Keyence Corporation, illustrated in FIG. 6 , is preparedas a measuring device, and the sample 10S is set in this measuringdevice. Specifically, one end of the long sample (magnetic tape MT) 10Sis fixed by a fixing portion 231. Next, as illustrated in FIG. 6 , thesample 10S is placed on five substantially cylindrical and rod-shapedsupport members 232 ₁ to 232 ₅. The sample 10S is placed on the supportmembers 232 ₁ to 232 ₅ such that the back surface thereof comes intocontact with the five support members 232 ₁ to 232 ₅. The five supportmembers 232 ₁ to 232 ₅ (particularly surfaces thereof) are all formed ofstainless steel SUS304, and have a surface roughness Rz (maximum height)of 0.15 μm to 0.3 μm.

Disposition of the five rod-shaped support members 232 ₁ to 232 ₅ willbe described with reference to FIG. 6 . As illustrated in FIG. 6 , thesample 10S is placed on the five support members 232 ₁ to 232 ₅.Hereinafter, the five support members 232 ₁ to 232 ₅ will be referred toas “first support member 232 ₁”, “second support member 232 ₂”, “thirdsupport member 232 ₃” (having a slit 232A), “fourth support member 232₄”, and “fifth support member 232 ₅” (closest to a weight 233) from aside closest to the fixing portion 231. Each of the five first to fifthsupport members 232 ₁ to 232 ₅ has a diameter of 7 mm. A distance d1between the first support member 232 ₁ and the second support member 232₂ (in particular, a distance between the central axes of these supportmembers) is 20 mm. A distance d2 between the second support member 232 ₂and the third support member 232 ₃ is 30 mm. A distance d3 between thethird support member 232 ₃ and the fourth support member 232 ₄ is 30 mm.A distance d4 between the fourth support member 232 ₄ and the fifthsupport member 232 ₅ is 20 mm.

Furthermore, the three support members 232 ₂ to 232 ₄ are disposed suchthat portions of the sample 10S between the second support member 232 ₂and the third support member 232 ₃ and between the third support member232 ₃ and the fourth support member 232 ₄ form a plane substantiallyperpendicular to the direction of gravity. Furthermore, the firstsupport member 232 ₁ and the second support member 232 ₂ are disposedsuch that the sample 10S forms an angle of θ1=30° with respect to thesubstantially perpendicular plane between the first support member 232 ₁and the second support member 232 ₂. Moreover, the fourth support member232 ₄ and the fifth support member 232 ₅ are disposed such that thesample 10S forms an angle of θ2=30° with respect to the substantiallyperpendicular plane between the fourth support member 232 ₄ and thefifth support member 232 ₅. Furthermore, among the five first to fifthsupport members 232 ₁ to 232 ₅, the third support member 232 ₃ is fixedso as not to rotate, but the other four first, second, fourth, and fifthsupport members 232 ₁, 232 ₂, 232 ₄, and 232 ₅ are all rotatable. Thesample 10S is held so as not to move in a width direction of the sample10S on the support members 232 ₁ to 232 ₅. Note that among the supportmembers 232 ₁ to 232 ₅, the support member 232 ₃ located between a lightemitter 234 and a light receiver 235 and located substantially at thecenter between the fixing portion 231 and a portion to which a load isapplied has the slit 232A. Light L is emitted from the light emitter 234to the light receiver 235 through the slit 232A. The slit 232A has aslit width of 1 mm, and the light L can pass through the slit 232Awithout being blocked by a frame of the slit 232A.

Subsequently, the measuring device is housed in a chamber controlledunder a constant environment in which the temperature is 25° C. and therelative humidity is 50%. Thereafter, the weight 233 for applying a loadof 0.2 N is attached to the other end of the sample 10S, and the sample10S is left in the environment for two hours. After being left for twohours, the width of the sample 10S is measured. Next, the weight forapplying a load of 0.2 N is changed to a weight for applying a load of0.6 N, and the width of the sample 10S is measured five minutes afterthe change. Finally, the weight is changed to a weight for applying aload of 1.0 N, and the width of the sample 10S is measured five minutesafter the change.

As described above, by adjusting the weight of the weight 233, a loadapplied to the sample 10S in a longitudinal direction thereof can bechanged. With each load applied, the light L is emitted from the lightemitter 234 toward the light receiver 235, and the width of the sample10S to which the load is applied in a longitudinal direction thereof ismeasured. The measurement of the width is performed in a state where thesample 10S is not curled. The light emitter 234 and the light receiver235 are included in the digital dimension measuring instrument LS-7000.

(Temperature Expansion Coefficient α)

The magnetic tape MT preferably has a temperature expansion coefficientα satisfying 6 [ppm/° C.]≤α≤8 [ppm/° C.]. When the temperature expansioncoefficient α is within the above range, the change in the width of themagnetic tape MT can be further suppressed by adjusting a tensionapplied to the magnetic tape MT in a longitudinal direction thereof bythe recording/reproducing device.

The temperature expansion coefficient α is determined as follows. First,the sample 10S is manufactured in a similar manner to the method formeasuring the dimensional change amount Δw, and the sample 10S is set ina measuring device similar to that in the method for measuring thedimensional change amount Δw. Thereafter, the measuring device is housedin a chamber controlled under a constant environment in which thetemperature is 29° C. and the relative humidity is 24%. Next, a load of0.2 N is applied to the sample 10S in a longitudinal direction thereof,and the sample 10S is conformed to the above environment. Thereafter,while the relative humidity is maintained at 24%, the temperature ischanged in the order of 45° C., 29° C., and 10° C., the width of thesample 10S is measured at 45° C. and 10° C., and the temperatureexpansion coefficient α is determined by the following formula. Notethat the measurement of the width of the sample 10S at the temperatureof 29° C. is performed in order to confirm whether or not abnormalityhas occurred in the measurement (in particular, in order to confirm thatthese three measurement results are linear). The measurement results arenot used in the following formula.

$\begin{matrix}{{a\lbrack {{ppm}/{^\circ}{C.}} \rbrack} = {\frac{{{D( {45{^\circ}{C.}} )}\lbrack{mm}\rbrack} - {{D( {10{^\circ}{C.}} )}\lbrack{mm}\rbrack}}{{D( {10{^\circ}{C.}} )}\lbrack{mm}\rbrack} \times \frac{1,000,000}{( {45\lbrack {{^\circ}{C.}} \rbrack} ) - ( {10\lbrack {{^\circ}{C.}} \rbrack} )}}} & \lbrack {{Math}.2} \rbrack\end{matrix}$(In which D (45° C.) and D (10° C.) indicate the widths of the sample10S at temperatures of 45° C. and 10° C., respectively.)(Humidity expansion coefficient β)

The magnetic tape MT preferably has a humidity expansion coefficient βsatisfying β≤5 [ppm/% RH]. When the humidity expansion coefficient β iswithin the above range, the change in the width of the magnetic tape MTcan be further suppressed by adjusting a tension applied to the magnetictape MT in a longitudinal direction thereof by the recording/reproducingdevice. The humidity expansion coefficient β is determined as follows.First, the sample 10S is manufactured in a similar manner to the methodfor measuring the dimensional change amount Δw, and the sample 10S isset in a measuring device similar to that in the method for measuringthe dimensional change amount Δw. Thereafter, the measuring device ishoused in a chamber controlled under a constant environment in which thetemperature is 29° C. and the relative humidity is 24%. Next, a load of0.2 N is applied to the sample 10S in a longitudinal direction thereof,and the sample 10S is conformed to the above environment. Thereafter,while the temperature of 29° C. is maintained, the relative humidity ischanged in the order of 80%, 24%, and 10%, the widths of the sample 10Sare measured at 80% and 10%, and the humidity expansion coefficient β isdetermined by the following formula. Note that the measurement of thewidth of the sample 10S at the humidity of 24% is performed in order toconfirm whether or not abnormality has occurred in the measurement (inparticular, in order to confirm that these three measurement results arelinear). The measurement results are not used in the following formula.

$\begin{matrix}{{\beta\lbrack {{ppm}/\%{RH}} \rbrack} = {\frac{{{D( {80\%} )}\lbrack{mm}\rbrack} - {{D( {10\%} )}\lbrack{mm}\rbrack}}{{D( {10\%} )}\lbrack{mm}\rbrack} \times \frac{1,000,000}{( {80\lbrack\%\rbrack} ) - ( {10\lbrack\%\rbrack} )}}} & \lbrack {{Math}.3} \rbrack\end{matrix}$(In which D (80%) and D (10%) indicate the widths of the sample 10S athumidities of 80% and 10%, respectively)(Poisson's ratio ρ)

The magnetic tape MT preferably has a Poisson's ratio ρ satisfying0.3≤ρ. When the Poisson's ratio ρ is within the above range, the changein the width of the magnetic tape MT can be further suppressed byadjusting a tension applied to the magnetic tape MT in a longitudinaldirection thereof by the recording/reproducing device.

The Poisson's ratio ρ is determined as follows. First, a magnetic tapeMT having a width of ½ inches is prepared and cut into a length of 150mm to manufacture a sample. Thereafter, a mark having a size of 6 mm×6mm is put on the central portion of the sample. Next, both end portionsof the sample in a longitudinal direction thereof are chucked such thatan inter-chuck distance is 100 mm, and an initial load of 2 N is appliedthereto. At this time, the length of the mark in the longitudinaldirection of the sample is taken as an initial length, and the width ofthe mark in a width direction of the sample is taken as an initialwidth. Subsequently, the sample is pulled at a tensile rate of 0.5mm/min using an Instron type universal tensile testing device, anddimensional change amounts of the length of the mark in the longitudinaldirection of the sample and the width of the mark in the width directionof the sample are measured with an image sensor manufactured by KeyenceCorporation. Thereafter, a Poisson's ratio ρ is determined by thefollowing formula.

$\begin{matrix}{\rho = \frac{\{ \frac{( {{Dimensional}{change}{amount}{of}{width}{of}{{mark}\lbrack{mm}\rbrack}} )}{( {{Initial}{{width}\lbrack{mm}\rbrack}} )} \}}{\{ \frac{( {{Dimensional}{change}{amount}{of}{length}{of}{{mark}{}\lbrack{mm}\rbrack}} )}{( {{Initial}{{length}\lbrack{mm}\rbrack}} )} \}}} & \lbrack {{Math}.4} \rbrack\end{matrix}$(Elastic limit value σ_(MD) in longitudinal direction)

An elastic limit value σ_(MD) of the magnetic tape MT in a longitudinaldirection thereof preferably satisfies 0.8 [N]≤σ_(MD). When the elasticlimit value σ_(MD) is within the above range, the change in the width ofthe magnetic tape MT can be further suppressed by adjusting a tensionapplied to the magnetic tape MT in a longitudinal direction thereof bythe recording/reproducing device. Furthermore, control on a drive sideis easy. An upper limit value of the elastic limit value σ_(MD) of themagnetic tape MT in a longitudinal direction thereof is not particularlylimited, but satisfies, for example, σ_(MD)≤5.0 [N]. Preferably, theelastic limit value σ_(MD) does not depend on a tensile rate V inelastic limit measurement. This is because with the elastic limit valueσ_(MD) not depending on the tensile rate V, a change in the width of themagnetic tape MT can be suppressed effectively without being affected bya traveling rate of the magnetic tape MT in the recording/reproducingdevice or a tension adjusting rate of the recording/reproducing deviceand responsiveness thereof. The elastic limit value σ_(MD) is set to adesired value, for example, by selecting curing condition of the baselayer 42, the recording layer 43, and the back layer 44 and selecting amaterial of the substrate 41. For example, as curing time of a baselayer forming coating material, a recording layer forming coatingmaterial, and a back layer forming coating material is lengthened, or asa curing temperature is raised, a reaction between a binder and a curingagent contained in each of these coating materials is accelerated. Thisimproves elastic characteristic and the elastic limit value σ_(MD).

The elastic limit value σ_(MD) is determined as follows. First, amagnetic tape MT having a width of ½ inches is prepared and cut into alength of 150 mm to manufacture a sample. Both ends of the sample in alongitudinal direction thereof are chucked in a universal tensiletesting device such that an inter-chuck distance λ₀ satisfies λ₀=100 mm.Next, the sample is pulled at a tensile rate of 0.5 mm/min, and a load σ(N) against an inter-chuck distance λ (mm) is continuously measured.Subsequently, using the obtained data of λ (mm) and σ (N), arelationship between Δλ (%) and σ (N) is graphed. However, Δλ (%) isdetermined by the following formula.Δλ (%)=((λ−λ₀/λ₀)×100

Next, in the above graph, a linear region in a region of σ≥0.2 N iscalculated, and a maximum load σ thereof is taken as the elastic limitvalue σ_(MD) (N).

(Interlayer Friction Coefficient μ)

An interlayer friction coefficient μ between a magnetic surface and aback surface preferably satisfies 0.20≤μ≤0.80. When the interlayerfriction coefficient μ is within the above range, it is possible tosuppress occurrence of winding deviation when the magnetic tape MT iswound around a reel (for example, the reel 13 in FIG. 2 ). Morespecifically, when the interlayer friction coefficient μ satisfiesμ<0.20, an interlayer friction between the magnetic surface of a portionlocated at an outermost periphery of the magnetic tape MT already woundaround a cartridge reel and the back surface of the magnetic tape MT tobe newly wound around the outside thereof is extremely low, and themagnetic tape MT to be newly wound easily deviates from the magneticsurface of the portion located at the outermost periphery of themagnetic tape MT already wound. Therefore, winding deviation of themagnetic tape MT occurs. Meanwhile, when the interlayer frictioncoefficient μ satisfies 0.80<μ, an interlayer friction between the backsurface of the magnetic tape MT to be just unwound from the outermostperiphery of the reel on a drive side and the magnetic surface of themagnetic tape MT located immediately below the back surface and stillwound around the drive reel is extremely high, and the back surface andthe magnetic surface are stuck to each other. Therefore, operation ofthe magnetic tape MT toward the cartridge reel is unstable, and thiscauses winding deviation of the magnetic tape MT. The interlayerfriction coefficient μ is determined as follows. First, a magnetic tapeMT having a width of ½ inches is wound around a cylinder having adiameter of one inch with the back surface thereof facing up, and themagnetic tape MT is fixed. Next, a magnetic tape MT having a width of ½inches is brought into contact with this cylinder at a holding angleθ(°)=180°+1° to 180°−10° such that the magnetic surface comes intocontact this time. One end of the tape MT is connected to a movablestrain gauge, and a tension T0=0.6 (N) is applied to the other end. Whenthe movable strain gauge is reciprocated at 0.5 mm/s eight times, straingauge readings T1 (N) to T8 (N) are measured in outward paths. Anaverage value of T4 to T8 is taken as T_(ave) (N). Thereafter, theinterlayer friction coefficient μ is determined by the followingformula.

$\begin{matrix}{\mu = {\frac{1}{( {\theta\lbrack{^\circ}\rbrack} ) \times ( {\pi/180} )} \times {\log_{e}( \frac{T_{ave}\lbrack N\rbrack}{T_{0}\lbrack N\rbrack} )}}} & \lbrack {{Math}.5} \rbrack\end{matrix}$(Surface roughness R_(b) of back surface)

Surface roughness of the back surface (surface roughness of the backlayer 44) R_(b) preferably satisfies R_(b)≤6.0 [nm]. When the surfaceroughness R_(b) of the back surface is within the above range,electromagnetic conversion characteristics can be improved.

The surface roughness R_(b) of the back surface is determined asfollows. First, a magnetic tape MT having a width of ½ inches isprepared, and the magnetic tape MT is stuck to slide glass with the backsurface thereof facing up to be used as a sample piece. Next, thesurface roughness of the back surface of the sample piece is measuredwith a non-contact roughness meter using the following opticalinterference.

Device: non-contact roughness meter using optical interference

(Non-contact surface/layer cross-sectional shape measurement systemVertScan R5500GL-M100-AC manufactured by Ryoka Systems Inc.)

Objective lens: 20 times (about 237 μm×178 μm field of view)

Resolution: 640 points×480 points

Measurement mode: phase

Wavelength filter: 520 nm

Surface correction: corrected with quadratic polynomial approximationsurface

As described above, the surface roughness is measured at five or morepoints in the longitudinal direction, and then an average value of therespective values of arithmetic average roughness Sa (nm) automaticallycalculated from surface profiles obtained at the respective points istaken as surface roughness R_(b) (nm) of the back surface.

(Coercive Force Hc)

The magnetic tape MT has a coercive force Hc of preferably 220 kA/m ormore and 310 kA/m or less, more preferably 230 kA/m or more and 300 kA/mor less, still more preferably 240 kA/m or more and 290 kA/m or lesswhen the coercive force Hc is measured in a thickness direction(perpendicular direction) of the magnetic tape MT. When the coerciveforce Hc is 220 kA/m or more, the coercive force Hc is sufficientlylarge. Therefore, it is possible to suppress deterioration of amagnetization signal recorded in an adjacent track due to a leakagemagnetic field from a recording head. Therefore, better SNR can beobtained. Meanwhile, when the coercive force Hc is 310 kA/m or less,saturation recording by a recording head is easy.

Therefore, better SNR can be obtained.

The coercive force Hc is determined as follows. First, a measurementsample is cut out from a long magnetic tape MT, and an M-H loop of theentire measurement sample is measured in a thickness direction of themeasurement sample (thickness direction of the magnetic tape MT) using avibrating sample magnetometer (VSM). Next, a coating film (base layer42, recording layer 43, or the like) is wiped away using acetone,ethanol, or the like. Only the substrate 41 is left for backgroundcorrection. An M-H loop of the substrate 41 is measured in a thicknessdirection of the substrate 41 (thickness direction of the magnetic tapeMT) using VSM. Thereafter, the M-H loop of the substrate 41 issubtracted from the M-H loop of the entire measurement sample to obtainan M-H loop after background correction. A coercive force Hc isdetermined from the obtained M-H loop. Note that each of themeasurements of the M-H loop is performed at 25° C. Furthermore, whenthe M-H loop is measured in the thickness direction (perpendiculardirection) of the magnetic tape MT, “demagnetizing field correction” isnot performed. Furthermore, according to the sensitivity of VSM used, aplurality of samples to be measured may be stacked on each other tomeasure the M-H loop.

(Ratio R Between Coercive Force Hc (50) and Coercive Force Hc (25))

A ratio R (=(Hc (50)/Hc (25))×100) between the coercive force Hc (50)measured in the thickness direction (perpendicular direction) of themagnetic tape MT at 50° C. and the coercive force Hc (25) measured inthe thickness direction of the magnetic tape MT at 25° C. is preferably95% or more, more preferably 96% or more, still more preferably 97% ormore, and particularly preferably 98% or more. When the ratio R is 95%or more, temperature dependency of the coercive force Hc is small, anddeterioration of SNR under a high temperature environment can besuppressed.

The coercive force Hc (25) is determined in a similar manner to theabove method for measuring a coercive force Hc. Furthermore, thecoercive force Hc (50) is determined in a similar manner to the abovemethod for measuring a coercive force Hc except that the M-H loops ofboth the measurement sample and the substrate 41 are measured at 50° C.

(Squareness Ratio S1 Measured in Traveling Direction)

The magnetic tape MT has a squareness ratio S1 of preferably 35% orless, more preferably 30% or less, still more preferably 25% or less,particularly preferably 20% or less, most preferably 15% or less whenthe squareness ratio S1 is measured in a traveling direction of themagnetic tape MT. When the squareness ratio S1 is 35% or less,perpendicular orientation of magnetic powder is sufficiently high.Therefore, better SNR can be obtained. Therefore, better electromagneticconversion characteristics can be obtained. Furthermore, the shape of aservo signal is improved, and it is easier to control a drive side.

The squareness ratio S1 is determined as follows. First, a measurementsample is cut out from a long magnetic tape MT, and an M-H loop of theentire measurement sample corresponding to a traveling direction(longitudinal direction) of the magnetic tape MT is measured using VSM.Next, a coating film (base layer 42, recording layer 43, or the like) iswiped away using acetone, ethanol, or the like. Only the substrate 41 isleft for background correction. An M-H loop of the substrate 41corresponding to a traveling direction of the substrate 41 (travelingdirection of the magnetic tape MT) is measured using VSM. Thereafter,the M-H loop of the substrate 41 is subtracted from the M-H loop of theentire measurement sample to obtain an M-H loop after backgroundcorrection. The squareness ratio S1 (%) is calculated by puttingsaturation magnetization Ms (emu) and residual magnetization Mr (emu) ofthe obtained M-H loop into the following formula. Note that each of themeasurements of the M-H loop is performed at 25° C. Furthermore,according to the sensitivity of VSM used, a plurality of samples to bemeasured may be stacked on each other to measure the M-H loop.Squareness ratio S1(%)=(Mr/Ms)×100(Squareness Ratio S2 Measured in Perpendicular Direction)

The magnetic tape MT has a squareness ratio S2 of preferably 65% ormore, more preferably 70% or more, still more preferably 75% or more,particularly preferably 80% or more, most preferably 85% or more whenthe squareness ratio S2 is measured in a perpendicular direction(thickness direction) of the magnetic tape MT. When the squareness ratioS2 is 65% or more, perpendicular orientation of magnetic powder issufficiently high. Therefore, better SNR can be obtained. Therefore,better electromagnetic conversion characteristics can be obtained.Furthermore, the shape of a servo signal is improved, and it is easierto control a drive side.

The squareness ratio S2 is determined in a similar manner to thesquareness ratio S1 except that the M-H loop is measured in theperpendicular direction (thickness direction) of the magnetic tape MTand the substrate 41. Note that in the measurement of the squarenessratio S2, when the M-H loop is measured in the perpendicular directionof the magnetic tape MT, “demagnetizing field correction” is notperformed.

The squareness ratios S1 and S2 are set to desired values, for example,by adjusting the intensity of a magnetic field applied to a recordinglayer forming coating material, application time of the magnetic fieldto the recording layer forming coating material, a dispersed state ofmagnetic powder in the recording layer forming coating material, theconcentration of a solid content in the recording layer forming coatingmaterial, and the like. Specifically, for example, as the intensity ofthe magnetic field is increased, the squareness ratio S1 becomessmaller, whereas the squareness ratio S2 becomes larger. Furthermore, asthe application time of the magnetic field is increased, the squarenessratio S1 becomes smaller, whereas the squareness ratio S2 becomeslarger. Furthermore, as the dispersed state of the magnetic powder isimproved, the squareness ratio S1 becomes smaller, whereas thesquareness ratio S2 becomes larger. Furthermore, as the concentration ofthe solid content decreases, the squareness ratio S1 becomes smaller,whereas the squareness ratio S2 becomes larger. Note that the adjustmentmethods may be used singly or in combination of two or more thereof.

Hc2/Hc1

A ratio Hc2/Hc1 between a coercive force Hc1 in a perpendiculardirection and a coercive force Hc2 in a longitudinal direction satisfiesHc2/Hc1≤0.8, preferably Hc2/Hc1≤0.75, more preferably Hc2/Hc1≤0.7, stillmore preferably Hc2/Hc1≤0.65, particularly preferably Hc2/Hc1≤0.6. Withthe coercive forces Hc1 and Hc2 satisfying Hc2/Hc1≤0.8, the degree ofperpendicular orientation of the magnetic powder can be increased.Therefore, a magnetization transition width can be reduced, and a highoutput signal can be obtained at the time of signal reproduction.Therefore, electromagnetic conversion characteristics (for example, C/N)can be improved. Note that as described above, with a small value ofHc2, magnetization reacts with high sensitivity due to a magnetic fieldin a perpendicular direction from a recording head.

Therefore, a good recording pattern can be formed.

In a case where the ratio Hc2/Hc1 satisfies Hc2/Hc1≤0.8, the averagethickness of the recording layer 43 is particularly effectively 90 nm orless. When the average thickness of the recording layer 43 exceeds 90nm, in a case where a ring type head is used as a recording head, alower region (region on the base layer 42 side) of the recording layer43 is magnetized in a longitudinal direction thereof, and it may beimpossible to magnetize the recording layer 43 uniformly in a thicknessdirection thereof. Therefore, even when the ratio Hc2/Hc1 satisfiesHc2/Hc1≤0.8 (that is, even when the degree of perpendicular orientationof magnetic powder is increased), it may be impossible to improveelectromagnetic conversion characteristics (for example, C/N). A lowerlimit value of Hc2/Hc1 is not particularly limited, but satisfies, forexample, 0.5≤Hc2/Hc1. Note that Hc2/Hc1 represents the degree ofperpendicular orientation of magnetic powder. The smaller the value ofHc2/Hc1 is, the higher the degree of perpendicular orientation of themagnetic powder is.

(SFD)

In a switching field distribution (SFD) curve of the magnetic tape MT, apeak ratio X/Y between a height X of a main peak and a height Y of asub-peak near the magnetic field zero is preferably 3.0 or more, morepreferably 5.0 or more, still more preferably 7.0 or more, particularlypreferably 10.0 or more, and most preferably 20.0 or more. When the peakratio X/Y is 3.0 or more, it is possible to suppress inclusion of alarge amount of low coercive force components unique to ε iron oxide(for example, soft magnetic particles or superparamagnetic particles) inmagnetic powder in addition to ε iron oxide particles contributing toactual recording.

Therefore, it is possible to suppress deterioration of a magnetizationsignal recorded in an adjacent track due to a leakage magnetic fieldfrom a recording head. Therefore, better SNR can be obtained. An upperlimit value of the peak ratio X/Y is not particularly limited, but isfor example, 100 or less.

The peak ratio X/Y is determined as follows. First, in a similar mannerto the above method for measuring a coercive force Hc, an M-H loop afterbackground correction is obtained. Next, an SFD curve is calculated fromthe obtained M-H loop. For calculating the SFD curve, a program attachedto a measuring machine may be used, or another program may be used. Bytaking an absolute value of a point where the calculated SFD curvecrosses the Y axis (dM/dH) as “Y” and taking the height of a main peakseen near a coercive force Hc in the M-H loop as “X”, the peak ratio X/Yis calculated. Note that the M-H loop is measured at 25° C. in a similarmanner to the above method for measuring a coercive force Hc.Furthermore, when the M-H loop is measured in the thickness direction(perpendicular direction) of the magnetic tape MT, “demagnetizing fieldcorrection” is not performed. Furthermore, according to the sensitivityof VSM used, a plurality of samples to be measured may be stacked oneach other to measure the M-H loop.

(Activation volume V_(act))

An activation volume V_(act) is preferably 8000 nm³ or less, morepreferably 6000 nm³ or less, still more preferably 5000 nm³ or less,particularly preferably 4000 nm³ or less, and most preferably 3000 nm³or less. When the activation volume V_(act) is 8000 nm³ or less, adispersed state of magnetic powder is good. Therefore, a bit inversionregion can be made steep, and it is possible to suppress deteriorationof a magnetization signal recorded in an adjacent track due to a leakagemagnetic field from a recording head. Therefore, it may be impossible toobtain better SNR.

The activation volume V_(act) is determined by the following formuladerived by Street & Woolley.V _(act)(nm ³)=k _(B) ×T×X _(irr)/(μ₀ ×Ms×S)(In which k_(B): Boltzmann's constant (1.38×10⁻³ J/K), T: temperature(K), X_(irr): irreversible susceptibility, μ₀: vacuum permeability, S:magnetic viscosity coefficient, Ms: saturation magnetization (emu/cm³))

The irreversible susceptibility X_(irr), the saturation magnetizationMs, and the magnetic viscosity coefficient S to be put in the aboveformula are determined using VSM as follows. Note that a measurementdirection using VSM is a thickness direction (perpendicular direction)of a magnetic tape MT. Furthermore, the measurement using VSM isperformed at 25° C. for a measurement sample cut out from a longmagnetic tape MT. Furthermore, when the M-H loop is measured in thethickness direction (perpendicular direction) of the magnetic tape MT,“demagnetizing field correction” is not performed. Furthermore,according to the sensitivity of VSM used, a plurality of samples to bemeasured may be stacked on each other to measure the M-H loop.

(Irreversible Susceptibility X_(irr))

The irreversible susceptibility X_(irr) is defined as an inclinationnear a residual coercive force Hr in the inclination of a residualmagnetization curve (DCD curve). First, a magnetic field of −1193 kA/m(15 kOe) is applied to the entire magnetic tape MT, and the magneticfield is returned to zero to obtain a residual magnetization state.Thereafter, a magnetic field of about 15.9 kA/m (200 Oe) is applied inthe opposite direction to return the magnetic field to zero again, and aresidual magnetization amount is measured. Thereafter, similarly,measurement of applying a magnetic field larger than the previouslyapplied magnetic field by 15.9 kA/m to return the magnetic field to zerois repeated, and a residual magnetization amount is plotted with respectto an applied magnetic field to form a DCD curve. From the obtained DCDcurve, a point where the magnetization amount is zero is taken as aresidual coercive force Hr, the DCD curve is differentiated, and theinclination of the DCD curve at each magnetic field is determined. Inthe inclination of this DCD curve, an inclination near the residualcoercive force Hr is X_(irr).

(Saturation Magnetization Ms)

First, the M-H loop of the entire magnetic tape MT (measurement sample)is measured in a thickness direction of the magnetic tape MT. Next, acoating film (base layer 42, recording layer 43, or the like) is wipedaway using acetone, ethanol, or the like. Only the substrate 41 is leftfor background correction. An M-H loop of the substrate 41 is measuredin a thickness direction thereof similarly. Thereafter, the M-H loop ofthe substrate 41 is subtracted from the M-H loop of the entire magnetictape MT to obtain an M-H loop after background correction. Ms (emu/cm³)is calculated from a value of saturation magnetization Ms (emu) of theobtained M-H loop and the volume (cm³) of the recording layer 43 in themeasurement sample. Note that the volume of the recording layer 43 isdetermined by multiplying the area of the measurement sample by anaverage thickness of the recording layer 43. Furthermore, according tothe sensitivity of VSM used, a plurality of samples to be measured maybe stacked on each other to measure the M-H loop. A method forcalculating the average thickness of the recording layer 43 necessaryfor calculating the volume of the recording layer 43 will be describedlater.

(Magnetic Viscosity Coefficient S)

First, a magnetic field of −1193 kA/m (15 kOe) is applied to the entiremagnetic tape MT (measurement sample), and the magnetic field isreturned to zero to obtain a residual magnetization state. Thereafter, amagnetic field equivalent to the value of the residual coercive force Hrobtained from the DCD curve is applied in the opposite direction. Amagnetization amount is continuously measured at constant time intervalsfor 1000 seconds in a state where a magnetic field is applied. Amagnetic viscosity coefficient S is calculated by comparing arelationship between time t and a magnetization amount M(t), obtained inthis way, with the following formula.M(t)=M0+S×ln(t)(In which M(t): magnetization amount at time t, M0: initialmagnetization amount, S: magnetic viscosity coefficient, ln(t): naturallogarithm of time)(BET Specific Surface Area)

A lower limit value of the BET specific surface area of the entiremagnetic tape MT in a state where a lubricant has been removed is 3.5m²/mg or more, preferably 4 m²/mg or more, more preferably 4.5 m²/mg ormore, and still more preferably 5 m²/mg or more. When the lower limitvalue of the BET specific surface area is 3.5 m²/mg or more, even afterrecording or reproduction is performed repeatedly (that is, even afterthe magnetic tape MT repeatedly travels while a magnetic head is incontact with a surface of the magnetic tape MT), it is possible tosuppress a decrease in the amount of a lubricant supplied to a spacebetween the recording layer 43 and the magnetic head. Therefore, anincrease in the coefficient of dynamic friction can be suppressed.

An upper limit value of the BET specific surface area of the entiremagnetic tape MT in a state where a lubricant has been removed ispreferably 7 m²/mg or less, more preferably 6 m²/mg or less, and stillmore preferably 5.5 m²/mg or less. When the upper limit value of the BETspecific surface area is 7 m²/mg or less, a lubricant can besufficiently supplied without being depleted even after traveling alarge number of times. Therefore, an increase in the coefficient ofdynamic friction can be suppressed.

An average pore diameter of the entire magnetic tape MT determined by aBJH method is 6 nm or more and 11 nm or less, preferably 7 nm or moreand 10 nm or less, and more preferably 7.5 nm or more and 10 nm or less.When the average pore diameter is 6 nm or more and 11 nm or less, theabove-described effect of suppressing the increase in the coefficient ofdynamic friction can be further improved.

The BET specific surface area and a pore distribution (pore volume andpore diameter of maximum pore volume at desorption) are determined asfollows. First, a magnetic tape MT is washed with hexane for 24 hours,and then cut into a size of 0.1265 m² to manufacture a measurementsample. Next, the BET specific surface area is determined using aspecific surface area/pore distribution measuring device. Furthermore, apore distribution (pore volume and pore diameter of maximum pore volumeat desorption) is determined by a BJH method. A measuring device andmeasuring conditions are indicated below.

Measuring device: 3 FLEX manufactured by Micromeritics Instrument Corp.

Measurement adsorbate: N₂ gas

Measurement pressure range (p/p0): 0 to 0.995

(Arithmetic Average Roughness Ra)

Arithmetic average roughness Ra of a magnetic surface is preferably 2.5nm or less, and more preferably 2.0 nm or less. When Ra is 2.5 nm orless, better SNR can be obtained.

The arithmetic average roughness Ra is determined as follows. First, asurface on which the recording layer 43 is disposed is observed using anatomic force microscope (AFM) (Dimension Icon manufactured by Bruker) toacquire a cross-sectional profile. Next, an arithmetic average roughnessRa is determined from the acquired cross-sectional profile according toJIS B0601:2001.

[Method for Manufacturing Magnetic Tape]

Next, an example of a method for manufacturing a magnetic tape MT havingthe above-described configuration will be described. First, by kneadingand dispersing nonmagnetic powder, a binder, and the like in a solvent,a base layer forming coating material is prepared.

Next, by kneading and dispersing magnetic powder, a binder, and the likein a solvent, a recording layer forming coating material is prepared.For preparing the recording layer forming coating material and the baselayer forming coating material, for example, the following solvents,dispersing devices, and kneading devices can be used.

Examples of the solvent used for preparing the above-described coatingmaterial include a ketone-based solvent such as acetone, methyl ethylketone, methyl isobutyl ketone, or cyclohexanone, an alcohol-basedsolvent such as methanol, ethanol, or propanol, an ester-based solventsuch as methyl acetate, ethyl acetate, butyl acetate, propyl acetate,ethyl lactate, or ethylene glycol acetate, an ether-based solvent suchas diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran,or dioxane, an aromatic hydrocarbon-based solvent such as benzene,toluene, or xylene, and a halogenated hydrocarbon-based solvent such asmethylene chloride, ethylene chloride, carbon tetrachloride, chloroform,or chlorobenzene. These solvents may be used singly, or may be used in amixture thereof appropriately.

Examples of a kneading device used for preparing the above-describedcoating material include a continuous twin-screw kneading machine, acontinuous twin-screw kneading machine capable of performing dilution inmultiple stages, a kneader, a pressure kneader, and a roll kneader, butare not particularly limited to these devices. Furthermore, examples ofa dispersing device used for preparing the above-described coatingmaterial include a roll mill, a ball mill, a horizontal sand mill, avertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill(for example, “DCP mill” manufactured by Eirich Co., Ltd.), ahomogenizer, and an ultrasonic wave dispersing machine, but are notparticularly limited to these devices.

Next, a base layer forming coating material is applied to one mainsurface of the substrate 41 and dried to form the base layer 42.Subsequently, by applying a recording layer forming coating materialonto the base layer 42 and drying the recording layer forming coatingmaterial, the recording layer 43 is formed on the base layer 42. Notethat during drying, magnetic powder is subjected to magnetic fieldorientation in a thickness direction of the substrate 41 by, forexample, a solenoid coil. Furthermore, during drying, the magneticpowder may be subjected to magnetic field orientation in a travelingdirection (longitudinal direction) of the substrate 41 by, for example,a solenoid coil, and then may be subjected to magnetic field orientationin a thickness direction of the substrate 41. After the formation of therecording layer 43, the back layer 44 is formed on the other mainsurface of the substrate 41. As a result, a magnetic tape MT isobtained.

Thereafter, the obtained magnetic tape MT is rewound around a largediameter core and subjected to a curing treatment. Finally, the magnetictape MT is subjected to a calendering treatment, and then cut into apredetermined width (for example, width of ½ inches). As a result, thetarget long and thin magnetic tape MT is obtained.

[Configuration of Recording/reproducing Device]

The recording/reproducing device 50 performs recording and reproductionof the magnetic tape MT having the above-described configuration. Therecording/reproducing device 50 can adjust a tension applied to themagnetic tape MT in a longitudinal direction thereof. Furthermore, therecording/reproducing device 50 can load the cartridge 10 thereon. Here,a case where the recording/reproducing device 50 can load one cartridge10 thereon will be described in order to facilitate the description.However, the recording/reproducing device 50 can load a plurality ofcartridges 10 thereon.

The recording/reproducing device 50 is connected to informationprocessing devices such as a server 71 and a personal computer(hereinafter referred to as “PC”) 72 through a network 70, and datasupplied from these information processing devices can be recorded inthe cartridge 10. Furthermore, in response to a request from theseinformation processing devices, data can be reproduced from thecartridge 10 and can be supplied to these information processingdevices. The shortest recording wavelength of the recording/reproducingdevice 50 is preferably 100 nm or less, more preferably 75 nm or less,still more preferably 60 nm or less, and particularly preferably 50 nmor less.

As illustrated in FIG. 1 , the recording/reproducing device 50 includesa spindle 51, a reel 52 on the recording/reproducing device 50 side, aspindle drive device 53, a reel drive device 54, a plurality of guiderollers 55, a head unit 56, a reader/writer 57 as a communication unit,a communication interface (hereinafter, I/F) 58, and a control device59.

The spindle 51 can mount the cartridge 10 thereon. A V-shaped servopattern is recorded in advance as a servo signal on the magnetic tapeMT. The reel 52 can fix a tip (leader pin 22) of the magnetic tape MTpulled out of the cartridge 10 through a tape loading mechanism (notillustrated).

The spindle drive device 53 rotates the spindle 51 in response to aninstruction from the control device 59. The reel drive device 54 rotatesthe reel 52 in response to an instruction from the control device 59.The plurality of guide rollers 55 guides traveling of the magnetic tapeMT such that a tape path formed between the cartridge 10 and the reel 52has a predetermined relative positional relationship with respect to thehead unit 56.

When data is recorded on the magnetic tape MT or data is reproduced fromthe magnetic tape MT, the spindle 51 and the reel 52 are rotationallydriven by the spindle drive device 53 and the reel drive device 54, andthe magnetic tape MT travels. The magnetic tape MT can be reciprocatedin a forward direction (a direction from the cartridge 10 side to thereel 52 side) and a backward direction (a direction from the reel 52side to the cartridge 10 side).

In the present embodiment, a tension applied to the magnetic tape MT ina longitudinal direction thereof can be adjusted at the time of datarecording or at the time of data reproduction by controlling rotation ofthe spindle 51 by the spindle drive device 53 and controlling rotationof the reel 52 by the reel drive device 54. Note that the adjustment ofa tension applied to the magnetic tape MT may be performed by control ofmovement of the guide rollers 55 instead of or in addition to thecontrol of rotation of the spindle 51 and the reel 52.

The reader/writer 57 can write first information and second informationin the cartridge memory 11 in response to an instruction from thecontrol device 59. Furthermore, the reader/writer 57 can read out thefirst information and the second information from the cartridge memory11 in response to an instruction from the control device 59. As acommunication method between the reader/writer 57 and the cartridgememory 11, for example, an ISO 14443 method is adopted. The secondinformation includes tension adjustment information. The tensionadjustment information is an example of data recording time information.

The control device 59 includes, for example, a control unit, a storageunit, and a communication unit. The control unit is constituted by, forexample, a central processing unit (CPU), and controls each unit of therecording/reproducing device 50 in accordance with a program stored inthe storage unit. For example, the control device 59 causes the headunit 56 to record a data signal supplied from an information processingdevice such as the server 71 or the PC 72 on the magnetic tape MT inresponse to a request from the information processing device.

Furthermore, the control device 59 causes the head unit 56 to reproducethe data signal recorded on the magnetic tape MT in response to arequest from an information processing device such as the server 71 orthe PC 72 and supplies the data signal to the information processingdevice. The storage unit includes a non-volatile memory in which variouskinds of data and various programs are recorded, and a volatile memoryused as a work area of the control unit. The various programs may beread from a portable recording medium such as an optical disk or aportable storage device such as a semiconductor memory, or may bedownloaded from a server device on a network.

The control device 59 causes the head unit 56 to read servo signalsrecorded in two adjacent servo bands SB at the time of recording data onthe magnetic tape MT or at the time of reproducing data from themagnetic tape MT. The control device 59 controls the position of thehead unit 56 such that the head unit 56 follows a servo pattern usingservo signals read from the two servo bands SB.

The control device 59 determines a distance (a distance in a widthdirection of the magnetic tape MT) d1 between two adjacent servo bandsSB at the time of recording data on the magnetic tape MT from areproduction waveform of the servo signals read from the two adjacentservo bands SB. Then, the reader/writer 57 writes the determineddistance in the memory 36.

The control device 59 determines a distance (a distance in a widthdirection of the magnetic tape MT) d2 between two adjacent servo bandsSB from a reproduction waveform of the servo signals read from the twoadjacent servo bands SB at the time of reproducing data from themagnetic tape MT. At the same time, the control device 59 causes thereader/writer 57 to read out the distance dl between the two adjacentservo bands SB, determined at the time of recording data on the magnetictape MT, from the memory 36. The control device 59 controls rotation ofthe spindle drive device 53 and the reel drive device 54 and adjusts atension applied to the magnetic tape MT in a longitudinal directionthereof such that a difference Δd between the distance dl between theservo bands SB determined at the time of recording data on the magnetictape MT and the distance d2 between the servo bands SB determined at thetime of reproducing data from the magnetic tape MT is within aprescribed range. The control of the tension adjustment is performed,for example, by feedback control.

The head unit 56 can record data on the magnetic tape MT in response toan instruction from the control device 59. Furthermore, the head unit 56can reproduce data recorded on the magnetic tape MT in response to aninstruction from the control device 59. The head unit 56 includes, forexample, two servo read heads and a plurality of data write/read heads.

The servo read heads read a magnetic field generated from a servo signalrecorded on the magnetic tape MT using a magneto resistive (MR) elementor the like, and can thereby reproduce the servo signal. A distancebetween the two servo read heads in a width direction thereof issubstantially the same as a distance between two adjacent servo bandsSB.

The data write/read heads are disposed at regular intervals in adirection from one servo read head to the other servo read head atpositions where the data write/read heads are sandwiched between the twoservo read heads. The data write/read heads can record data on themagnetic tape MT by a magnetic field generated from a magnetic gap.Furthermore, the data write/read heads read a magnetic field generatedfrom data recorded on the magnetic tape MT using an MR element or thelike, and can thereby reproduce the data.

The communication I/F 58 is for communicating with an informationprocessing device such as the server 71 or the PC 72, and is connectedto the network 70.

[Operation of Recording/reproducing Device at the Time of DataRecording]

Hereinafter, an example of operation of the recording/reproducing device50 at the time of data recording will be described with reference toFIG. 7 .

First, the control device 59 loads the cartridge 10 on therecording/reproducing device 50 (step S11). Next, the control device 59controls rotation of the spindle 51 and the reel 52 and causes themagnetic tape MT to travel while applying a prescribed tension to themagnetic tape MT in a longitudinal direction thereof. Then, the controldevice 59 causes a servo read head of the head unit 56 to read a servosignal, and causes a data write/read head of the head unit 56 to recorddata on the magnetic tape MT (step S12).

At this time, the head unit 56 records data on a data band DB with thedata write/read head of the head unit 56 while tracing two adjacentservo bands SB with the two servo read heads of the head unit 56.

Next, the control device 59 determines a distance d1 between twoadjacent servo bands SB at the time of data recording from areproduction waveform of a servo signal read by a servo read head of thehead unit 56 (step S13). Next, the control device 59 causes thereader/writer 57 to write the distance d1 between the servo bands SB atthe time of data recording in the cartridge memory 11 (step S14). Thecontrol device 59 may continuously measure the distance d1 between theservo bands SB and write distance d1 in the cartridge memory 11, or maymeasure the distance d1 between the servo bands SB at regular intervalsand write the distance d1 in the cartridge memory 11. In a case wherethe distance d1 between the servo bands SB is measured at regularintervals and written in the cartridge memory 11, the amount ofinformation written in the memory 36 can be reduced.

[Operation of Recording/reproducing Device at the Time of DataReproduction]

Hereinafter, an example of operation of the recording/reproducing device50 at the time of data reproduction will be described with reference toFIG. 8 .

First, the control device 59 loads the cartridge 10 on therecording/reproducing device 50 (step S21). Next, the control device 59causes the reader/writer 57 to read out a distance dl between servobands at the time of recording from the cartridge memory 11 (step S22).

Next, the control device 59 controls rotation of the spindle 51 and thereel 52 and causes the magnetic tape MT to travel while applying aprescribed tension to the magnetic tape MT in a longitudinal directionthereof. Then, the control device 59 causes a servo read head of thehead unit 56 to read a servo signal, and causes a data write/read headof the head unit 56 to reproduce data from the magnetic tape MT (stepS23).

Next, the control device 59 calculates a distance d2 between twoadjacent servo bands SB at the time of data reproduction from areproduction waveform of a servo signal read by a servo read head of thehead unit 56 (step S24).

Next, the control device 59 determines whether or not a difference Δdbetween the distance d1 between the servo bands read in step S22 and thedistance d2 between the servo bands SB calculated in step S24 is withina prescribed range (step S25).

In step S25, in a case where it is determined that the difference Δd iswithin the prescribed range, the control device 59 controls rotation ofthe spindle 51 and the reel 52 so as to maintain a prescribed tension(step S26).

Meanwhile, in step S25, in a case where it is determined that thedifference Δd is not within a prescribed range, the control device 59controls rotation of the spindle 51 and the reel 52 so as to reduce thedifference Δd, adjusts a tension applied to the traveling magnetic tapeMT, and returns the process to step S24 (step S27).

[Effect]

As described above, in the first embodiment, the average thickness t_(T)of the magnetic tape MT satisfies t_(T)≤5.5 [μm], and the dimensionalchange amount Δw of the magnetic tape MT in a width direction thereofwith respect to a tension change of the magnetic tape MT in alongitudinal direction thereof satisfies 650 [ppm/N]≤Δw. Furthermore,the memory (storage unit) 36 of the cartridge memory 11 has an area(second storage area 36B) in which width-related information related tothe width of the magnetic tape MT at the time of data recording iswritten. As a result, even in a case where the width of the magnetictape MT fluctuates for some reasons (for example, a change intemperature or humidity), the width-related information is used at thetime of data reproduction, the recording/reproducing device 50 adjusts atension applied to the magnetic tape MT in a longitudinal directionthereof, and a change in the width of the magnetic tape MT can bethereby suppressed. Therefore, even in a case where the width of themagnetic tape MT fluctuates for some reasons, a decrease in reliabilityof reproduction can be suppressed.

2. Second Embodiment

[Configuration of Recording/reproducing Device]

FIG. 9 is a schematic diagram illustrating an example of a configurationof a recording/reproducing system 100A according to a second embodimentof the present disclosure. The recording/reproducing system 100Aincludes a cartridge 10 and a recording/reproducing device 50A.

The recording/reproducing device 50 further includes a thermometer 60and a hygrometer 61.

The thermometer 60 measures the temperature around a magnetic tape MT(cartridge 10) and outputs the temperature to a control device 59.Furthermore, the hygrometer 40 measures the humidity around the magnetictape MT (cartridge 10) and outputs the humidity to the control device59.

The control device 59 causes the thermometer 39 and the hygrometer 40 tomeasure a temperature Tm1 and a humidity H1 around the magnetic tape MT(cartridge 10) at the time of recording data on the magnetic tape MT,and writes the temperature Tm1 and the humidity H1 in a cartridge memory11 through a reader/writer 57. The temperature Tm1 and the humidity H1are examples of environmental information around the magnetic tape MT.

The control device 59 determines a tension Tn1 applied to the magnetictape MT in a longitudinal direction thereof on the basis of drive dataof the spindle 51 and the reel 52 at the time of recording data on themagnetic tape MT, and writes the tension Tn1 in the cartridge memory 11through the reader/writer 57.

The control device 59 determines a distance d1 between two adjacentservo bands SB from a reproduction waveform of servo signals read fromthe two adjacent servo bands SB at the time of recording data on themagnetic tape MT. Then, the control device 59 calculates a width W1 ofthe magnetic tape MT at the time of data recording on the basis of thedistance d1, and causes the reader/writer 57 to write the width W1 in amemory 36.

The control device 59 causes the thermometer 39 and the hygrometer 40 tomeasure a temperature Tm2 and a humidity H2 around the magnetic tape MT(cartridge 10) at the time of reproducing data from the magnetic tapeMT.

The control device 59 determines a tension Tn2 applied to the magnetictape MT in a longitudinal direction thereof on the basis of drive dataof the spindle 51 and the reel 52 at the time of reproducing data fromthe magnetic tape MT.

The control device 59 determines a distance d2 between two adjacentservo bands SB from a reproduction waveform of servo signals read fromtwo adjacent servo bands SB at the time of reproducing data from themagnetic tape MT. Then, the control device 59 calculates a width W2 ofthe magnetic tape MT at the time of data reproduction on the basis ofthe distance d2. The control device 59 reads the temperature Tm1, thehumidity H1, the tension Tn1, and the width W1 written at the time ofdata recording from the cartridge memory 11 through the reader/writer 57at the time of reproducing data from the magnetic tape MT. Then, thecontrol device 59 controls a tension applied to the magnetic tape MTusing the temperature Tm1, the humidity H1, the tension Tn1, and thewidth W1 at the time of recording data, and the temperature Tm2, thehumidity H2, the tension Tn2, and the width W2 at the time ofreproducing data such that the width W2 of the magnetic tape MT at thetime of data reproduction is equal to or substantially equal to thewidth W1 of the magnetic tape at the time of data recording.

A controller 35 of the cartridge memory 11 stores the temperature Tm1,the humidity H1, the tension Tn1, and the width W1 received from therecording/reproducing device 50A through an antenna coil 31 in thesecond storage area 36B of the memory 36. The controller 35 of thecartridge memory 11 reads out the temperature Tm1, the humidity H1, thetension Tn1, and the width W1 from the memory 36 in response to arequest from the recording/reproducing device 50A, and transmits thetemperature Tm1, the humidity H1, the tension Tn1, and the width W1 tothe recording/reproducing device 50A through the antenna coil 31.

[Operation of Recording/reproducing Device at the Time of DataRecording]

Hereinafter, an example of operation of the recording/reproducing device50A at the time of data recording will be described with reference toFIG. 10 .

First, the control device 59 loads the cartridge 10 on therecording/reproducing device 50 (step S101). Next, the control device 59controls rotation of the spindle 51 and the reel 52 and causes themagnetic tape MT to travel while applying a prescribed tension to themagnetic tape MT in a longitudinal direction thereof. Then, the controldevice 59 causes a head unit 56 to record data on the magnetic tape MT(step S102).

Next, the control device 59 acquires the temperature Tm1 and thehumidity H1 (environmental information) around the magnetic tape MT atthe time of data recording from the thermometer 39 and the hygrometer 40(step S103).

Next, the control device 59 calculates the tension Tn1 applied to themagnetic tape MT in a longitudinal direction thereof at the time of datarecording on the basis of drive data of the spindle 51 and the reel 52at the time of data recording (step S104).

Next, the control device 59 determines a distance d1 between twoadjacent servo bands SB from a reproduction waveform of a servo signalread by a servo read head of the head unit 56. Next, the control device59 calculates the width W1 of the magnetic tape MT at the time of datarecording on the basis of the distance d1 (step S105).

Next, the control device 59 causes the reader/writer 57 to write thetemperature Tm1, the humidity H1, the tension Tn1, and the width W1 ofthe magnetic tape MT as data recording time information in the cartridgememory 11 (step S106).

[Operation of Recording/reproducing Device at the Time of DataReproduction]

Hereinafter, an example of operation of the recording/reproducing device50A at the time of data reproduction will be described with reference toFIG. 11 .

First, the control device 59 loads the cartridge 10 on therecording/reproducing device 50 (step S111). Next, the control device 59causes the reader/writer 57 to read out data recording time information(temperature Tm1, humidity H1, tension Tn1, and width W1 of the magnetictape MT) written in the cartridge memory 11 from the cartridge memory 11and acquires the data recording time information (step S112). Next, thecontrol device 59 acquires information regarding the current temperatureTm2 and information regarding the current humidity H2 around themagnetic tape MT at the time of data reproduction from the thermometer39 and the hygrometer 40 (step S113).

Next, the control device 59 calculates a temperature difference TmD(TmD=Tm2−Tm1) between the temperature Tm1 at the time of data recordingand the temperature Tm2 at the time of data reproduction (step S114).Furthermore, the control device 59 calculates a humidity difference HD(HD=H2−H1) between the humidity H1 at the time of data recording and thehumidity H2 at the time of data reproduction (step S115).

Next, the control device 59 multiplies the temperature difference TmD bya coefficient α (TmD×α), and multiplies the humidity difference HD by acoefficient β (HD×β) (step S116). The coefficient α indicates how muchthe tension applied to the magnetic tape MT should be changed ascompared to the tension Tn1 at the time of data recording for atemperature difference of 1° C. The coefficient β indicates how much thetension applied to the magnetic tape MT should be changed as compared tothe tension Tn1 at the time of data recording for a humidity differenceof 1%.

Next, the control device 59 adds the value of TmD×α and the value ofHD×β to the tension Tn1 at the time of data recording, and therebycalculates the tension Tn2 to be applied to the magnetic tape MT in alongitudinal direction thereof at the time of data reproduction(currently) (step S117).Tn2=Tn1+TmD×α+HD×β

After determining the tension Tn2 applied to the magnetic tape MT at thetime of data reproduction, the control device 59 controls rotation ofthe spindle 51 and the reel 52, and controls traveling of the magnetictape MT such that the magnetic tape MT travels with the tension Tn2.Then, the control device 59 causes a data write/read head of the headunit 56 to reproduce data recorded in a data track Tk while causing aservo read head of the head unit 56 to read a servo signal of a servoband SB.

At this time, since the width of the magnetic tape MT is adjusted to thewidth at the time of data recording by adjusting a tension applied tothe magnetic tape MT, the data write/read head of the head unit 56 canbe accurately positioned with respect to the data track Tk. As a result,even in a case where the width of the magnetic tape MT fluctuates due tosome causes (for example, fluctuation of temperature or humidity), datarecorded on the magnetic tape MT can be reproduced accurately.

Note that the value of the tension Tn2 to be applied to the magnetictape MT is higher at the time of data reproduction (currently) if thetemperature at the time of data reproduction is higher than thetemperature at the time of data recording. For this reason, in a casewhere the temperature is higher and the width of the magnetic tape MT iswider than that at the time of data recording, the width of the magnetictape MT can be narrowed to reproduce the same width as that at the timeof data reproduction.

Conversely, the value of the tension Tn2 to be applied to the magnetictape MT is lower at the time of data reproduction (currently) if thetemperature at the time of data reproduction is lower than thetemperature at the time of data recording. For this reason, in a casewhere the temperature is lower and the width of the magnetic tape MT isnarrower than that at the time of data recording, the width of themagnetic tape MT can be widened to reproduce the same width as that atthe time of data reproduction.

Furthermore, the value of the tension Tn2 to be applied to the magnetictape MT is higher at the time of data reproduction (currently) if thehumidity at the time of data reproduction is higher than the humidity atthe time of data recording. For this reason, in a case where thehumidity is higher and the width of the magnetic tape MT is wider thanthat at the time of data recording, the width of the magnetic tape MTcan be narrowed to reproduce the same width as that at the time of datareproduction.

Conversely, the value of the tension Tn2 to be applied to the magnetictape MT is lower at the time of data reproduction (currently) if thehumidity at the time of data reproduction is lower than the humidity atthe time of data recording. For this reason, in a case where thehumidity is lower and the width of the magnetic tape MT is narrower thanthat at the time of data recording, the width of the magnetic tape MTcan be widened to reproduce the same width as that at the time of datareproduction.

Here, in order to determine the tension Tn2 to be applied to themagnetic tape MT at the time of data reproduction, in addition to thetemperature Tm1, the humidity H1, and the tension Tn1 applied to themagnetic tape MT (or instead of the tension Tn1) at the time of datarecording, information regarding the width W1 of the magnetic tape MT atthe time of data recording may be further used.

Also in this case, similarly, the control device 59 calculates thetemperature difference TmD (TmD=Tm2−Tm1) and the humidity difference HD(HD=H2−H1). Then, the control device 59 multiplies the temperaturedifference TmD by a coefficient γ (TmD×γ), and multiplies the humiditydifference HD by a coefficient δ (HD×6) (step S118).

Here, the coefficient γ indicates how much the width of the magnetictape MT fluctuates for a temperature difference of 1° C. (indicates anexpansion coefficient per unit length (in a width direction) based ontemperature). Furthermore, the coefficient δ indicates how much thewidth of the magnetic tape MT fluctuates for a humidity difference of 1%(indicates an expansion coefficient per unit length (in a widthdirection) based on humidity).

Next, the control device 59 predicts the current width W2 of themagnetic tape MT at the time of data reproduction on the basis of thepast width W1 of the magnetic tape MT at the time of data recordingaccording to the following formula.W2=W1(1+TmD×γ+HD2×δ)

Next, the control device 59 calculates a difference WD between thecurrent width W2 of the magnetic tape MT at the time of datareproduction and the past width W1 of the magnetic tape MT at the timeof data recording (WD=W2−W1=W1 (TmD×γ+HD2×δ)). Then, the control device59 multiplies the width difference WD by a coefficient ε, adds theobtained value to the tension Tn1 applied to the magnetic tape MT at thetime of data recording, and calculates the tension Tn2 applied to themagnetic tape MT at the time of data reproduction.Tn2=Tn1+WD×ε

Here, the coefficient ε represents a tension applied to the magnetictape MT in s longitudinal direction thereof, necessary to change thewidth of the magnetic tape MT by a unit distance.

After determining the tension Tn2 applied to the magnetic tape MT at thetime of data reproduction, the control device 59 controls rotation ofthe spindle 51 and the reel 52, and controls traveling of the magnetictape MT such that the magnetic tape MT travels with the tension Tn2.Then, the control device 59 causes a data write/read head of the headunit 56 to reproduce data recorded in a data track Tk while causing aservo read head of the head unit 56 to read a servo signal of a servoband SB.

Even in a case where the tension Tn2 is determined by such a method, ina case where the width of the magnetic tape MT fluctuates due to somecauses (for example, fluctuation of temperature or humidity), datarecorded on the magnetic tape MT can be reproduced accurately.

[Effect]

As described above, in the second embodiment, since the data recordingtime information of the magnetic tape MT is stored in the cartridgememory 11, by using this information at the time of data reproduction,the width of the magnetic tape MT can be appropriately adjusted.Therefore, even in a case where the width of the magnetic tape MTfluctuates for some reasons, the data recorded on the magnetic tape MTcan be accurately reproduced.

Furthermore, in the present embodiment, the temperature Tm1 and thehumidity H1 (environmental information) around the magnetic tape MT atthe time of data recording are written as data recording timeinformation. Therefore, the fluctuation of the width of the magnetictape MT and the fluctuation of the width of the data track Tk due to thefluctuation of the temperature and the humidity can be appropriatelydealt with.

3. Modification

(Modification 1)

In the above-described embodiments, the case where an ε iron oxideparticle has a two-layered shell portion has been described. However,the ε iron oxide particle may have a single layer shell portion. In thiscase, the shell portion has a similar configuration to the first shellportion. However, an ε iron oxide particle preferably has a two-layeredshell portion as in the above-described embodiments from a viewpoint ofsuppressing characteristic deterioration of the ε iron oxide particle.

(Modification 2)

In the above-described embodiments, the case where an ε iron oxideparticle has a core-shell structure has been described. However, the εiron oxide particle may contain an additive instead of the core-shellstructure, or may have a core-shell structure and contain an additive.In this case, some of Fe atoms in the ε iron oxide particles arereplaced with an additive. Even by inclusion of an additive in an ε ironoxide particle, a coercive force Hc of the entire ε iron oxide particlescan be adjusted to a coercive force Hc suitable for recording.Therefore, recordability can be improved. The additive is a metalelement other than iron, preferably a trivalent metal element, morepreferably at least one of Al, Ga, and In, and still more preferably atleast one of Al and Ga.

Specifically, the ε iron oxide containing an additive is anε-Fe_(2−x)M_(x)O₃ crystal (in which M represents a metal element otherthan iron, preferably a trivalent metal element, more preferably atleast one of Al, Ga, and In, and still more preferably at least one ofAl and Ga, and x satisfies, for example, 0<x<1).

(Modification 3)

In the above-described embodiments, the case where magnetic powdercontains powder of ε iron oxide particles has been described. However,the magnetic powder may contain powder of nanoparticles containinghexagonal ferrite (hereinafter referred to as “hexagonal ferriteparticles”) instead of the powder of ε iron oxide particles. Thehexagonal ferrite particle has, for example, a hexagonal plate shape ora substantially hexagonal plate shape. The hexagonal ferrite preferablycontains at least one of Ba, Sr, Pb, and Ca, more preferably at leastone of Ba and Sr. Specifically, the hexagonal ferrite may be, forexample, barium ferrite or strontium ferrite. The barium ferrite mayfurther contain at least one of Sr, Pb, and Ca in addition to Ba. Thestrontium ferrite may further contain at least one of Ba, Pb, and Ca inaddition to Sr. More specifically, the hexagonal ferrite has an averagecomposition represented by a general formula MFe₁₂O₁₉. However, Mrepresents at least one metal of Ba, Sr, Pb, and Ca, preferably at leastone metal of Ba and Sr. M may represent a combination of Ba and one ormore metals selected from the group consisting of Sr, Pb, and Ca.Furthermore, M may represent a combination of Sr and one or more metalsselected from the group consisting of Ba, Pb, and Ca. In the abovegeneral formula, some of Fe atoms may be replaced with another metalelement. In a case where the magnetic powder contains powder ofhexagonal ferrite particles, the average particle size of the magneticpowder is preferably 30 nm or less, more preferably 12 nm or more and 25nm or less, and still more preferably 15 nm or more and 22 nm or less.When the average particle size of the magnetic powder is 30 nm or less,good electromagnetic conversion characteristics (for example, C/N) canbe obtained in a magnetic tape MT having a high recording density.Meanwhile, when the average particle size of the magnetic powder is 12nm or more, dispersibility of the magnetic powder is further improved,and better electromagnetic conversion characteristics (for example, C/N)can be obtained. In a case where the magnetic powder contains powder ofhexagonal ferrite particles, the average aspect ratio of the magneticpowder is similar to those of the above-described embodiments.

Note that the average particle size and the average aspect ratio of themagnetic powder is determined as follows. First, a magnetic tape MT tobe measured is processed by an FIB method or the like to manufacture athin piece, and a cross section of the thin piece is observed with TEM.Next, 50 particles of the magnetic powder oriented at an angle of 75degrees or more with respect to a horizontal direction are randomlyselected from the photographed TEM photograph, and a maximum platethickness DA of each of the particles of the magnetic powder ismeasured. Subsequently, the maximum plate thicknesses DA of the measured50 particles of the magnetic powder are simply averaged (arithmeticallyaveraged) to determine an average maximum plate thickness DAave.

Next, a surface of the recording layer 43 of the magnetic tape MT isobserved with TEM. Next, 50 particles of the magnetic powder arerandomly selected from the photographed TEM photograph, and a maximumplate diameter DB of each of the particles of the magnetic powder ismeasured. Here, the maximum plate diameter DB means the largest distanceamong distances between two parallel lines drawn from all angles so asto come into contact with an outline of each of the particles of themagnetic powder (so-called maximum Feret diameter). Subsequently, themaximum plate diameters DB of the measured 50 particles of the magneticpowder are simply averaged (arithmetically averaged) to determine anaverage maximum plate diameter DBave. The average maximum plate diameterDBave determined in this manner is taken as the average particle size ofthe magnetic powder. Next, an average aspect ratio (DBave/DAave) of themagnetic powder is determined from the average maximum plate thicknessDAave and the average maximum plate diameter DBave.

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, the average particle volume of the magnetic powder ispreferably 5900 nm³ or less, more preferably 500 nm³ or more and 3400nm³ or less, and still more preferably 1000 nm³ or more and 2500 nm³ orless. When the average particle volume of the magnetic powder is 5900nm³ or less, a similar effect to that in a case where the averageparticle size of the magnetic powder is 30 nm or less can be obtained.Meanwhile, when the average particle volume of the magnetic powder is500 nm³ or more, a similar effect to a case where the average particlesize of the magnetic powder is 12 nm or more can be obtained.

Note that the average particle volume of the magnetic powder isdetermined as follows. First, the average maximum plate thickness DAaveand the average maximum plate diameter DBave are determined in a similarmanner to the above-described method for calculating the averageparticle size of the magnetic powder. Next, an average particle volume Vof the magnetic powder is determined by the following formula.V=3√{square root over (3/8)}×DAave×DBave²(Modification 4)

In the above-described embodiments, the case where magnetic powdercontains powder of ε iron oxide particles has been described. However,the magnetic powder may contain powder of nanoparticles containingCo-containing spinel ferrite (hereinafter referred to as “cobalt ferriteparticles”) instead of the powder of ε iron oxide particles. The cobaltferrite particle preferably has uniaxial anisotropy. The cobalt ferriteparticle has, for example, a cubic shape or a substantially cubic shape.The Co-containing spinel ferrite may further contain at least one of Ni,Mn, Al, Cu, and Zn in addition to Co.

The Co-containing spinel ferrite has, for example, an averagecomposition represented by the following formula (1).Co _(x) M _(y) Fe ₂ O _(z)  (1)(In formula (1), M represents, for example, at least one metal of Ni,Mn, Al, Cu, and Zn). x represents a value within a range of 0.4≤x≤1.0. yrepresents a value within a range of 0≤y≤0.3. Provided that x and ysatisfy a relationship of (x+y)≤1.0. z represents a value within a rangeof 3≤z≤4. Some of Fe atoms may be replaced with another metal element.)

In a case where the magnetic powder contains powder of cobalt ferriteparticles, the average particle size of the magnetic powder ispreferably 25 nm or less, and more preferably 8 nm or more and 23 nm orless. When the average particle size of the magnetic powder is 25 nm orless, good electromagnetic conversion characteristics (for example, C/N)can be obtained in a magnetic tape MT having a high recording density.Meanwhile, when the average particle size of the magnetic powder is 8 nmor more, dispersibility of the magnetic powder is further improved, andbetter electromagnetic conversion characteristics (for example, C/N) canbe obtained. In a case where the magnetic powder contains powder ofcobalt ferrite particles, the average aspect ratio of the magneticpowder is similar to those of the above-described embodiments.Furthermore, a method for calculating the average particle size and theaverage aspect ratio of the magnetic powder is determined in a similarmanner to those of the above-described embodiments.

The average particle volume of the magnetic powder is preferably 15000nm³ or less, and more preferably 500 nm³ or more and 12000 nm³ or less.When the average particle volume of the magnetic powder is 15000 nm³ orless, a similar effect to that in a case where the average particle sizeof the magnetic powder is 25 nm or less can be obtained. Meanwhile, whenthe average particle volume of the magnetic powder is 500 nm³ or more, asimilar effect to a case where the average particle size of the magneticpowder is 8 nm or more can be obtained. Note that a method forcalculating the average particle volume of the magnetic powder issimilar to the method for calculating the average particle volume of themagnetic powder (the method for calculating the average particle volumein a case where the ε iron oxide particle has a cubic shape or asubstantially cubic shape) in the above-described embodiments.

(Modification 5)

The magnetic tape MT may be used for a library device. In this case, thelibrary device can adjust a tension applied to the magnetic tape MT in alongitudinal direction thereof, and may include a plurality of therecording/reproducing devices 50 in the first embodiment.

(Modification 6)

The magnetic tape MT may be used for a servo writer. In other words, theservo writer adjusts a tension applied to the magnetic tape MT in alongitudinal direction thereof at the time of recording a servo signalor the like, and the width of the magnetic tape MT may be thereby keptconstant or substantially constant. In this case, the servo writer mayinclude a detection device that detects the width of the magnetic tapeMT, and may adjust a tension applied to the magnetic tape MT in alongitudinal direction thereof on the basis of a detection result of thedetection device.

(Modification 7)

The magnetic tape MT is not limited to a perpendicular recording typemagnetic recording medium, and may be a horizontal recording typemagnetic recording medium. In this case, acicular magnetic powder suchas metal magnetic powder may be used as magnetic powder.

(Modification 8)

In the above-described first embodiment, the case where a distancebetween servo bands SB is used as width-related information related tothe magnetic tape MT at the time of data recording has been described,but the width of the magnetic tape MT may be used.

In this case, the control device 59 calculates the width W1 of themagnetic tape MT from the distance dl between the servo bands SB at thetime of data recording, and causes the reader/writer 57 to write thewidth W1 in the cartridge memory 11.

The control device 59 reads out the width W1 of the magnetic tape MT atthe time of data recording from the cartridge memory 11 at the time ofdata reproduction, and calculates the width W2 of the magnetic tape MTat the time of data reproduction from the distance d2 between the servobands SB at the time of data reproduction. Then, the control device 59calculates a difference ΔW between the width W1 of the magnetic tape MTat the time of data recording and the width W2 of the magnetic tape MTat the time of data reproduction, and determines whether or not thedifference ΔW is within a prescribed range.

In a case where the difference Δd is within the prescribed range, thecontrol device 59 controls rotational drive of the spindle 51 and thereel 52 so as to maintain a prescribed tension. Meanwhile, in a casewhere the difference Δd is not within the prescribed range, the controldevice 59 controls rotational drive of the spindle 51 and the reel 52such that the difference Δd falls within the prescribed range, andadjusts a tension applied to the traveling magnetic tape MT.

(Modification 9)

In the above-described second embodiment, the case where all of thetemperatures Tm1 and Tm2, the humidities H1 and H2, the tensions Tn1 andTn2, and the widths W1 and W2 are used as the data recording timeinformation has been described. However, as the data recording timeinformation, any one of the temperatures Tm1 and Tm2, the humidities H1and H2, the tensions Tn1 and Tn2, and the widths W1 and W2 may be used,or a combination of any two or three thereof may be used.

Not only information at the time of data recording (temperature Tm1,humidity H1, tension Tn₁, and width W1) but also information at the timeof data reproduction (temperature Tm2, humidity H2, tension Tn2, andwidth W2) may be stored in the cartridge memory 11. For example, theinformation at the time of data reproduction is used when data in themagnetic tape MT is reproduced at another opportunity after the data isreproduced.

(Modification 10)

In the above-described first and second embodiments, the case in whichthe magnetic tape MT is an application type magnetic tape in which abase layer, a recording layer, and the like are manufactured by anapplication step (wet process) has been described. However, the magnetictape MT may be a thin film type magnetic tape in which a base layer, arecording layer, and the like are manufactured by a technique ofmanufacturing a vacuum thin film (dry process) such as sputtering. In acase of the thin film type magnetic tape, an average thickness t_(m) ofthe recording layer satisfies preferably 9 [nm]≤t_(m)≤90 [nm], morepreferably 9 [nm]≤t_(m)≤20 [nm], still more preferably 9 [nm]≤t_(m)≤15[nm]. When the average thickness t_(m) of the recording layer 43satisfies 9 [nm]≤t_(m)≤90 [nm], electromagnetic conversioncharacteristics can be improved.

EXAMPLES

Hereinafter, the present disclosure will be described specifically withExamples, but the present disclosure is not limited only to theseExamples.

In the following Examples and Comparative Examples, an average thicknessT_(sub) of a substrate, an average thickness t_(T) of a magnetic tape, adimensional change amount Δw of a magnetic tape in a width directionthereof with respect to a tension change of the magnetic tape in alongitudinal direction thereof, a temperature expansion coefficient α ofa magnetic tape, a humidity expansion coefficient β of a magnetic tape,a Poisson's ratio ρ of a magnetic tape, an elastic limit value σ_(MD) ofa magnetic tape in a longitudinal direction thereof, a tensile rate V inelastic limit measurement, an average thickness t_(m) of a recordinglayer, a squareness ratio S2, an average thickness t_(b) of a backlayer, surface roughness R_(b) of a back layer, and an interlayerfriction coefficient μ between a magnetic surface and a back surface aredetermined by the measurement method described in the first embodiment.However, as described later, in Example 11, a tensile rate V at the timeof measuring an elastic limit value amp in a longitudinal direction wasdifferent from that in the first embodiment.

Example 1

(Step of Preparing Recording Layer Forming Coating Material)

A recording layer forming coating material was prepared as follows.First, a first composition having the following formulation was kneadedwith an extruder. Next, the kneaded first composition and a secondcomposition having the following formulation were added to a stirringtank equipped with a disper, and were premixed. Subsequently, themixture was further subjected to sand mill mixing, and was subjected toa filter treatment to prepare a recording layer forming coatingmaterial.

(First Composition)

Powder of ε iron oxide nanoparticles (ε-Fe₂O₃ crystal particles): 100parts by mass

Vinyl chloride-based resin (cyclohexanone solution 30% by mass): 10parts by mass

(Degree of polymerization: 300, Mn=10000, OSO₃K=0.07 mmol/g andsecondary OH=0.3 mmol/g were contained as polar groups)

Aluminum oxide powder: 5 parts by mass

(α-Al₂O₃, average particle diameter: 0.2 μm)

Carbon black: 2 parts by mass

(Manufactured by Tokai Carbon Co., Ltd., trade name: Seast TA)

(Second Composition)

Vinyl chloride-based resin: 1.1 parts by mass

(Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 121.3 parts by mass

Toluene: 121.3 parts by mass

Cyclohexanone: 60.7 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curingagent and 2 parts by mass of myristic acid were added to the recordinglayer forming coating material prepared as described above.(Step of Preparing Base Layer Forming Coating Material)

A base layer forming coating material was prepared as follows. First, athird composition having the following formulation was kneaded with anextruder. Next, the kneaded third composition and a fourth compositionhaving the following formulation were added to a stirring tank equippedwith a disper, and were premixed. Subsequently, the mixture was furthersubjected to sand mill mixing, and was subjected to a filter treatmentto prepare a base layer forming coating material.

(Third Composition)

Acicular iron oxide powder: 100 parts by mass

(α-Fe₂O₃, average long axis length 0.15 μm)

Vinyl chloride-based resin: 55.6 parts by mass

(Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)

Carbon black: 10 parts by mass

(Average particle diameter 20 nm)

(Fourth Composition)

Polyurethane-based resin UR8200 (manufactured by Toyobo Co., Ltd.): 18.5parts by mass

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 108.2 parts by mass

Toluene: 108.2 parts by mass

Cyclohexanone: 18.5 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Nippon Polyurethane Industry Co., Ltd.) as a curingagent and 2 parts by mass of myristic acid were added to the base layerforming coating material prepared as described above.(Step of Preparing Back Layer Forming Coating Material)

A back layer forming coating material was prepared as follows. Thefollowing raw materials were mixed in a stirring tank equipped with adisper, and were subjected to filter treatment to prepare a back layerforming coating material.

Carbon black (manufactured by Asahi Corporation, trade name: #80): 100parts by mass

Polyester polyurethane: 100 parts by mass

(Trade name: N-2304, manufactured by Nippon Polyurethane Industry Co.,Ltd.)

Methyl ethyl ketone: 500 parts by mass

Toluene: 400 parts by mass

Cyclohexanone: 100 parts by mass

(Film Forming Step)

Using the coating material prepared as described above, a base layerhaving an average thickness to of 1.0 μm and a recording layer having anaverage thickness t_(m) of 90 nm were formed as follows on a longpolyethylene naphthalate film (hereinafter referred to as “PEN film”)having an average thickness T_(sub) of 3.8 μm as a substrate(nonmagnetic support). First, a base layer forming coating material wasapplied onto a film and dried to form a base layer on the film. Next, arecording layer forming coating material was applied onto the base layerand dried to form a recording layer on the base layer. Note that themagnetic powder was subjected to magnetic field orientation in athickness direction of the film by a solenoid coil when the recordinglayer forming coating material was dried. Furthermore, time during whicha magnetic field was applied to the recording layer forming coatingmaterial was adjusted, and a squareness ratio S2 of a magnetic tape in athickness direction (perpendicular direction) thereof was set to 65%.

Subsequently, a back layer having an average thickness t_(b) of 0.6 μmwas applied to the film on which the base layer and the recording layerhad been formed, and was dried. Then, the film on which the base layer,the recording layer, and the back layer had been formed was subjected toa curing treatment. Subsequently, the film was subjected to acalendering treatment to smooth a surface of the recording layer. Atthis time, a condition (temperature) of the calendering treatment wasadjusted such that an interlayer friction coefficient μ between amagnetic surface and the back surface was 0.5. Thereafter, the film wassubjected to a recuring treatment to obtain a magnetic tape having anaverage thickness t_(T) of 5.5 μm.

(Cutting Step)

The magnetic tape obtained as described above was cut into a width of ½inches (12.65 mm). As a result, a desired long magnetic tape havingcharacteristics illustrated in Tables 1 and 2 was obtained.

(Servo Pattern Recording Step)

On the magnetic tape obtained as described above, two or more rows ofV-shaped magnetic patterns (servo patterns) were recorded in parallel toa longitudinal direction thereof.

(Cartridge Manufacturing Step)

First, as a cartridge, one having an area in which tension adjustmentinformation is written in a cartridge memory and capable of writing thetension adjustment information in the area and reading out the tensionadjustment information from the area was prepared. Next, a magnetic tapehaving rows of magnetic patterns recorded thereon was wound around thecartridge.

Thereafter, the cartridge was loaded on a recording/reproducing device,prescribed data was recorded therein, and at least two of the aboveV-shaped magnetic pattern rows were simultaneously reproduced.Alternatively, data was not recorded but at least two of the aboveV-shaped magnetic pattern rows were only reproduced. From the shape of areproduction waveform of each of the rows, an interval d1 between themagnetic pattern rows at the time of data recording was measured atregular intervals (at an interval of 1 m), and the positions and theinterval were written in the cartridge memory. As a result, a targetcartridge was obtained.

Example 2

The thickness of the PEN film was made thinner than that of Example 1such that the dimensional change amount Δw was 750 [ppm/N]. A cartridgewas obtained in a similar manner to Example 1 except for this.

Example 3

The thickness of the PEN film was made thinner than that of Example 1such that the dimensional change amount Δw was 800 [ppm/N], and theaverage thicknesses of the back layer and the base layer were thinned. Acartridge was obtained in a similar manner to Example 1 except for this.

Example 4

The thickness of the PEN film was made thinner than that of Example 1such that the dimensional change amount Δw was 800 [ppm/N], and theaverage thicknesses of the back layer and the base layer were thinned.Moreover, curing treatment conditions of the film on which the baselayer, the recording layer, and the back layer had been formed wereadjusted. A cartridge was obtained in a similar manner to Example 1except for this.

Example 5

A cartridge was obtained in a similar manner to Example 4 except thatthe composition of the base layer forming coating material was changedsuch that the temperature expansion coefficient α was 8 [ppm/° C.].

Example 6

A cartridge was obtained in a similar manner to Example 4 except thatthin barrier layers were formed on both surfaces of the PEN film suchthat the humidity expansion coefficient β was 3 [ppm/% RH].

Example 7

A cartridge was obtained in a similar manner to Example 4 except thatthe composition of the back layer forming coating material was changedsuch that the Poisson's ratio ρ was 0.31.

Example 8

A cartridge was obtained in a similar manner to Example 4 except thatthe composition of the back layer forming coating material was changedsuch that the Poisson's ratio ρ was 0.35.

Example 9

A cartridge was obtained in a similar manner to Example 7 except thatthe curing condition of the film on which the base layer, the recordinglayer, and the back layer had been formed were adjusted such that theelastic limit value σ_(MD) in a longitudinal direction was 0.80 [N].

Example 10

A cartridge was obtained in a similar manner to Example 7 except thatthe curing condition of the film on which the base layer, the recordinglayer, and the back layer had been formed and the recuring conditionwere adjusted such that the elastic limit value a σ_(MD) in alongitudinal direction was 3.50 [N].

Example 11

A magnetic tape was obtained in a similar manner to Example 9. Then, theelastic limit value σ_(MD) of the obtained magnetic tape was measured bychanging the tensile rate V to 5 mm/min when the elastic limit valueσ_(MD) in a longitudinal direction was measured. As a result, theelastic limit value σ_(MD) in the longitudinal direction was 0.80 [N]with no change with respect to the elastic limit value σ_(MD) in thelongitudinal direction with the tensile rate V of 0.5 mm/min (Example9).

Example 12

A cartridge was obtained in a similar manner to Example 7 except thatthe coating thickness of the recording layer forming coating materialwas changed such that the average thickness t_(m) of the recording layerwas 40 nm.

Example 13

(SUL Film Forming Step)

First, under the following film forming conditions, a CoZrNb layer (SUL)having an average thickness of 10 nm was formed on a surface of a longpolymer film as a nonmagnetic support. Note that a PEN film was used asthe polymer film.

Film forming method: DC magnetron sputtering method

Target: CoZrNb target

Gas species: Ar

Gas pressure: 0.1 Pa

(First Seed Layer Forming Step)

Next, a TiCr layer (first seed layer) having an average thickness of 5nm was formed on the CoZrNb layer under the following film formingconditions.

Sputtering method: DC magnetron sputtering method

Target: TiCr target

Ultimate degree of vacuum: 5×10⁻⁵ Pa

Gas species: Ar

Gas pressure: 0.5 Pa

(Second Seed Layer Forming Step)

Next, a NiW layer (second seed layer) having an average thickness of 10nm was formed on the TiCr layer under the following film formingconditions.

Sputtering method: DC magnetron sputtering method

Target: NiW target

Ultimate degree of vacuum: 5×10⁻⁵ Pa

Gas species: Ar

Gas pressure: 0.5 Pa

(First Base Layer Forming Step)

Next, a Ru layer (first base layer) having an average thickness of 10 nmwas formed on the NiW layer under the following film forming conditions.

Sputtering method: DC magnetron sputtering method

Target: Ru target

Gas species: Ar

Gas pressure: 0.5 Pa

(Second Base Layer Forming Step)

Next, on the Ru layer, a Ru layer (second base layer) having an averagethickness of 20 nm was formed under the following film formingconditions.

Sputtering method: DC magnetron sputtering method

Target: Ru target

Gas species: Ar

Gas pressure: 1.5 Pa

(Recording Layer Forming Step)

Next, a (CoCrPt)-(SiO₂) layer (recording layer) having an averagethickness t_(m) of 9 nm was formed on the Ru layer under the followingfilm forming conditions.

Film forming method: DC magnetron sputtering method

Target: (CoCrPt)-(SiO₂) target

Gas species: Ar

Gas pressure: 1.5 Pa

(Protective Layer Forming Step)

Next, a carbon layer (protective layer) having an average thickness of 5nm was formed on the recording layer under the following film formingconditions.

Film forming method: DC magnetron sputtering method

Target: carbon target

Gas species: Ar

Gas pressure: 1.0 Pa

(Lubricating Layer Forming Step)

Next, a lubricant was applied onto the protective layer to form alubricating layer.

(Back Layer Forming Step)

Next, a back layer forming coating material was applied to the surfaceopposite to the recording layer and dried to form a back layer having anaverage thickness t_(T) of 0.3 μm. As a result, a magnetic tape havingan average thickness t_(T) of 4.0 μm was obtained.

(Cutting Step)

The magnetic tape obtained as described above was cut into a width of ½inches (12.65 mm). As a result, a desired long magnetic tape havingcharacteristics illustrated in Tables 1 and 2 was obtained.

A servo pattern was recorded and a cartridge was manufactured in asimilar manner to Example 1 except that the magnetic tape obtained asdescribed above was used, and the cartridge was obtained.

Example 14

A cartridge was obtained in a similar manner to Example 7 except thatthe coating thickness of the back layer forming coating material waschanged such that the average thickness t_(b) of the back layer was 0.3μm.

Example 15

A cartridge was obtained in a similar manner to Example 7 except thatthe composition (addition amount of the inorganic filler (carbon black))of the back layer forming coating material was changed such that thesurface roughness R_(b) of the back layer was 3 [nm].

Example 16

A cartridge was obtained in a similar manner to Example 7 except thatthe condition (temperature) of the calendering treatment was adjustedsuch that the interlayer friction coefficient μ between the magneticsurface and the back surface was 0.2.

Example 17

A cartridge was obtained in a similar manner to Example 7 except thatthe condition (temperature) of the calendering treatment was adjustedsuch that the interlayer friction coefficient μ between the magneticsurface and the back surface was 0.8.

Example 18

A cartridge was obtained in a similar manner to Example 7 except thatthe coating thickness of the recording layer forming coating materialwas changed such that the average thickness t_(m) of the recording layerwas 110 nm.

Example 19

A cartridge was obtained in a similar manner to Example 7 except thatthe composition (addition amount of the inorganic filler (carbon black))of the back layer forming coating material was changed such that thesurface roughness R_(b) of the back layer was 7 [nm].

Example 20

A cartridge was obtained in a similar manner to Example 7 except thatthe condition (temperature) of the calendering treatment was adjustedsuch that the interlayer friction coefficient μ between the magneticsurface and the back surface was 0.18.

Example 21

A cartridge was obtained in a similar manner to Example 7 except thatthe condition (temperature) of the calendering treatment was adjustedsuch that the interlayer friction coefficient μ between the magneticsurface and the back surface was 0.82.

Example 22

A cartridge was obtained in a similar manner to Example 7 except thattime during which a magnetic field was applied to the magnetic layerforming coating material was adjusted, and the squareness ratio S2 ofthe magnetic tape in a thickness direction (perpendicular direction)thereof was set to 73%.

Example 23

A cartridge was obtained in a similar manner to Example 7 except thattime during which a magnetic field was applied to the magnetic layerforming coating material was adjusted, and the squareness ratio S2 ofthe magnetic tape in a thickness direction (perpendicular direction)thereof was set to 80%.

Example 24

A cartridge was obtained in a similar manner to Example 10 except thatthe curing condition of the film on which the base layer, the recordinglayer, and the back layer had been formed and the recuring conditionwere adjusted such that the elastic limit value a MD in the longitudinaldirection was 5.00 [N].

Example 25

A cartridge was obtained in a similar manner to Example 7 except thatbarium ferrite (BaFe₁₂O₁₉) nanoparticles were used instead of the ε ironoxide nanoparticles.

Example 26

A PEN film having higher stretching strength in the width direction thanthe PEN film of Example 7 was used such that the dimensional changeamount Δw was 670 [ppm/N]. A cartridge was obtained in a similar mannerto Example 25 except for this.

Example 27

A PEN film having higher stretching strength in the width direction thanthe PEN film of Example 1 was used such that the dimensional changeamount Δw was 650 [ppm/N]. A cartridge was obtained in a similar mannerto Example 1 except for this.

Comparative Example 1

A PEN film having higher stretching strength in the width direction thanthe PEN film of Example 26 and having an average thickness T_(sub) of4.0 μm was used such that the dimensional change amount Δw was 630[ppm/N]. A cartridge was obtained in a similar manner to Example 1except for this.

Comparative Example 2

A PEN film having higher stretching strength in the width direction thanthe PEN film of Example 26 and having an average thickness T_(sub) of5.0 μm was used such that the dimensional change amount Δw was 500[ppm/N]. Furthermore, the average thickness t_(b) of the back layer was0.4 μm. A cartridge was obtained in a similar manner to Example 1 exceptfor this.

Reference Examples 1 to 26 and Comparative Examples 3 to 5

First, a magnetic tape was obtained in a similar to Examples 1 to 27 andComparative Examples 1 and 2, and then rows of V-shaped magneticpatterns were recorded on the magnetic tape. Subsequently, as acartridge, one in which writing of tension adjustment information andreading out of the tension adjustment information might be impossiblewas prepared. Next, a magnetic tape having rows of magnetic patternsrecorded thereon was wound around the cartridge. Thereafter, thecartridge was loaded on a recording/reproducing device, and prescribeddata was recorded therein. As a result, a target cartridge was obtained.

(Judgment of Amount of Change in Tape Width (1))

First, each of the cartridges of Examples 1 to 27 and ComparativeExamples 1 and 2 was loaded on a recording/reproducing device, and amagnetic tape was reproduced and reciprocated while a tension applied tothe magnetic tape in a longitudinal direction thereof was adjusted. Atthis time, the recording/reproducing device adjusted the tension asfollows. In other words, two or more V-shaped magnetic pattern rows werereproduced together with data. From the shape of a reproduction waveformof each of the rows, an interval d2 between the magnetic pattern rows atthe time of data reproduction was measured continuously (at every pointhaving servo position information (specifically, approximately every 6mm), and an interval d1 between the magnetic pattern rows at the time ofdata recording was read out from the cartridge memory. Then, rotationaldrive of a spindle drive device and a reel drive device was controlledsuch that the interval d2 between the magnetic pattern rows at the timeof data reproduction approached the interval d1 between the magneticpattern rows at the time of data recording. A tension applied to themagnetic tape in a longitudinal direction thereof was adjustedautomatically. A measurement value for each of the reciprocations of allthe intervals between the magnetic pattern rows was taken as an“interval d2 between the measured magnetic pattern rows”, and a maximumvalue of a difference between the interval d2 and a “known interval d1between magnetic pattern rows in traveling previously” was taken as a“change in tape width”.

Furthermore, the recording/reproducing device caused a magnetic tape tobe reciprocated in a thermo-hygrostat bath. A reciprocation rate was 5m/sec. The temperature and humidity during the reciprocation weregradually and repeatedly changed independently of the abovereciprocation within a temperature range of 10° C. to 45° C. and arelative humidity range of 10% to 80% according to a previously createdenvironmental change program (10° C. 10%→29° C. 80%→10° C. 10% wasrepeated twice, in which change from 10° C. 10% to 29° C.80% was made intwo hours, and change from 29° C. 80% to 10° C. 10% was made in twohours). This evaluation was repeated until the “previously createdenvironmental change program” was completed. After the evaluation wascompleted, an average value (simple average) was calculated using allthe absolute values of the respective “changes in tape width” obtainedat the respective reciprocations, and was taken as an “effective amountof change in tape width” of the tape. Judgment was made on eachcartridge according to a deviation from an ideal of the “effectiveamount of change in tape width” (a smaller deviation is more desirable),and a judgment value with any one of eight ratings was given to eachcartridge. Note that an evaluation “8” indicated the most desirablejudgment result, and an evaluation “1” indicated the most undesirablejudgment result. In a magnetic tape with any one of the eight ratings,the following state is observed during traveling of the tape.

8: No abnormality occurs

7: A slight increase in error rate is observed during traveling

6: A serious increase in error rate is observed during traveling

5: It may be impossible to read a servo signal during traveling, and aservo signal is read again to a slight degree (one or two times)

4: It may be impossible to read a servo signal during traveling, and aservo signal is read again to a medium degree (up to 10 times)

3: It may be impossible to read a servo signal during traveling, and aservo signal is read again to a serious degree (more than 10 times)

2: It may be impossible to read a servo signal, and a tape stopsoccasionally due to a system error

1: It may be impossible to read a servo signal, and a tape stopsimmediately due to a system error

(Judgment of Amount of Change in Tape Width (2))

Each of the cartridges of Reference Examples 1 to 26 and ComparativeExamples 1 to 3 was loaded on a recording/reproducing device, and amagnetic tape was reproduced and reciprocated while a tension applied tothe magnetic tape in a longitudinal direction thereof was adjusted. Atthis time, the recording/reproducing device adjusted the tension asfollows. In other words, two or more V-shaped magnetic pattern rows werereproduced together with data. From the shape of a reproduction waveformof each of the rows, an interval d2 between the magnetic pattern rows atthe time of data reproduction was measured continuously. Then,rotational drive of a spindle drive device and a reel drive device wascontrolled such that the interval d2 between the magnetic pattern rowsat the time of data reproduction approached a prescribed interval d3. Atension applied to the magnetic tape in a longitudinal direction thereofwas adjusted automatically. Judgment was made on each cartridgeaccording to a deviation from an ideal of the “effective amount ofchange in tape width” in a similar manner to judgment of amount ofchange in tape width (1) except for this, and a judgment value with anyone of eight ratings was given to each cartridge. Note that theprescribed interval d3 is an interval of a known magnetic pattern rowserving as a reference when a tension applied to the magnetic tape in alongitudinal direction thereof is adjusted, and is stored in advance inthe control device of the recording/reproducing device.

(Evaluation of electromagnetic conversion characteristics)

First, a reproduction signal of a magnetic tape used in each of thecartridges of Examples 1 to 27 and Comparative Examples 1 and 2 wasacquired using a loop tester (manufactured by MicroPhysics, Inc.).Acquisition conditions of the reproduction signal will be describedbelow.

head: GMR head

speed: 2 m/s

signal: single recording frequency (10 MHz)

Recording current: optimum recording current

Next, the reproduction signal was captured with a span of 0 to 20 MHz(resolution band width=100 kHz, VBW=30 kHz) with a spectrum analyzer.Next, a peak of the captured spectrum was taken as a signal amount S.Floor noise excluding the peak was integrated to obtain a noise amountN. A ratio S/N between the signal amount S and the noise amount N wasdetermined as a signal-to-noise ratio (SNR). Next, the determined SNRwas converted into a relative value (dB) based on the SNR of ComparativeExample 1 as a reference medium. Next, it was judged whetherelectromagnetic conversion characteristics were good or poor as followsusing the SNR (dB) obtained as described above.

Good: The SNR of a magnetic tape is equal to or larger than the SNR (=0(dB)) of the evaluation reference sample (Comparative Example 1).

Poor: The SNR of a magnetic tape is less than the SNR (=0 (dB)) of theevaluation reference sample (Comparative Example 1).

(Evaluation of Winding Deviation)

First, a cartridge sample after the above “judgment of amount of changein tape width (1)” was prepared. Next, the reel around which the tapewas wound was taken out from the cartridge sample, and an end face ofthe wound tape was visually observed. Note that the reel had a flange,at least one flange was transparent or translucent, and the tape windingstate inside could be observed through the flange.

As a result of the observation, in a case where the end face of the tapewas not flat, and there were steps or protrusions of the tape, it wasassumed that there was a winding deviation in the tape. Furthermore, itwas assumed that the “winding deviation” was poorer as more “steps andprotrusions of the tape were observed. The above judgment was made foreach sample. The winding deviation state of each sample was compared tothe winding deviation state of Comparative Example 1 as a referencemedium, and it was judged whether the state was good or poor as follows.

Good: a case where the winding deviation state of a sample is equal toor less than that of the reference sample (Comparative Example 1)

Poor: a case where the winding deviation state of a sample is more thanthat of the reference sample (Comparative example 1)

Tables 1 and 2 illustrate configurations and evaluation results of thecartridges of Examples 1 to 27 and Comparative Examples 1 and 2.

TABLE 1 Magnetic T_(sub) t_(T) Δw α [ppm/ β [ppm/ σ_(MD) V material [μm][μm] [ppm/N] ° C.] % RH] ρ [N] [mm/min] Example 1 ε iron 3.8 5.5 705 5.95.2 0.29 0.75 0.5 oxide Example 2 ε iron 3.3 5.0 750 5.9 5.2 0.29 0.750.5 oxide Example 3 ε iron 3.2 4.5 800 5.9 5.2 0.29 0.75 0.5 oxideExample 4 ε iron 3.2 4.5 800 6.0 5.0 0.29 0.75 0.5 oxide Example 5 εiron 3.2 4.5 800 8.0 5.0 0.29 0.75 0.5 oxide Example 6 ε iron 3.2 4.6800 6.0 3.0 0.29 0.75 0.5 oxide Example 7 ε iron 3.2 4.5 800 6.0 5.00.31 0.75 0.5 oxide Example 8 ε iron 3.2 4.5 800 6.0 5.0 0.35 0.75 0.5oxide Example 9 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.80 0.5 oxide Example10 ε iron 3.2 4.5 800 6.0 5.0 0.31 3.50 0.5 oxide Example 11 ε iron 3.24.5 800 6.0 5.0 0.31 0.80 5.0 oxide Example 12 ε iron 3.2 4.4 800 6.05.0 0.31 0.75 0.5 oxide Example 13 (CoCrPt)- 3.6 4.0 800 6.0 5.0 0.310.75 0.5 (SiO₂) Example 14 ε iron 3.2 4.4 800 6.0 5.0 0.31 0.75 0.5oxide Example 15 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.75 0.5 oxide Example16 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.75 0.5 oxide Example 17 ε iron 3.24.5 800 6.0 5.0 0.31 0.75 0.5 oxide Example 18 ε iron 3.2 4.5 800 6.05.0 0.31 0.75 0.5 oxide Example 19 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.750.5 oxide Example 20 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.75 0.5 oxideExample 21 ε iron 3.2 4.5 800 6.0 5.0 0.31 0.75 0.5 oxide Example 22 εiron 3.2 4.5 800 6.0 5.0 0.31 0.75 0.5 oxide Example 23 ε iron 3.2 4.5800 6.0 5.0 0.31 0.75 0.5 oxide Example 24 ε iron 3.2 4.5 800 6.0 5.00.31 5.00 0.5 oxide Example 25 BaFe₁₂O₁₉ 3.2 4.5 800 6.0 5.0 0.31 0.750.5 Example 26 BaFe₁₂O₁₉ 3.2 4.5 670 6.0 5.0 0.31 0.75 0.5 Example 27 εiron 3.8 5.5 650 5.9 5.2 0.29 0.75 0.5 oxide Comparative BaFe₁₂O₁₉ 4.05.7 630 6.0 5.0 0.3 0.75 0.5 Example 1 Comparative BaFe₁₂O₁₉ 5.0 6.5 5006.5 5.0 0.3 0.75 0.5 Example 2

TABLE 2 Presence or absence of Electro- Judgment storage area magneticof amount of tension conversion of change t_(m) S2 t_(u) t_(b) R_(b)adjustment character- in tape Winding [nm] [%] [μm] [μm] [nm] μinformation istics width (1) deviation Example 1 90 65 1.0 0.6 6 0.5Present Good 8 Good Example 2 90 65 1.0 0.6 6 0.5 Present Good 8 GoodExample 3 90 65 0.9 0.3 6 0.5 Present Good 8 Good Example 4 90 65 0.90.3 6 0.5 Present Good 8 Good Example 5 90 65 0.9 0.3 6 0.5 Present Good8 Good Example 6 90 65 1.0 0.3 6 0.5 Present Good 8 Good Example 7 90 650.9 0.3 6 0.5 Present Good 8 Good Example 8 90 65 0.9 0.3 6 0.5 PresentGood 8 Good Example 9 90 65 0.9 0.3 6 0.5 Present Good 8 Good Example 1090 65 0.9 0.3 6 0.5 Present Good 8 Good Example 11 90 65 0.9 0.3 6 0.5Present Good 8 Good Example 12 40 65 0.9 0.3 6 0.5 Present Good 8 GoodExample 13 9 98 — 0.3 6 0.5 Present Good 8 Good Example 14 90 65 0.8 0.36 0.5 Present Good 8 Good Example 15 90 65 0.9 0.3 3 0.5 Present Good 8Good Example 16 90 65 0.9 0.3 6 0.2 Present Good 8 Good Example 17 90 650.9 0.3 3 0.8 Present Good 8 Good Example 18 110 65 0.9 0.3 6 0.5Present Poor 8 Good Example 19 90 65 0.9 0.3 7 0.5 Present Poor 8 GoodExample 20 90 65 0.9 0.3 6 0.18 Present Good 8 Poor Example 21 90 65 0.90.3 6 0.82 Present Good 8 Poor Example 22 90 73 0.9 0.3 6 0.5 PresentGood 8 Good Example 23 90 80 0.9 0.3 6 0.5 Present Better 8 Good Example24 90 65 0.9 0.3 6 0.5 Present Good 8 Good Example 25 90 65 0.9 0.3 60.5 Present Good 8 Good Example 26 90 65 0.9 0.3 6 0.5 Present Good 8Good Example 27 90 65 1.0 0.6 6 0.5 Present Good 8 Good Comparative 9065 1.0 0.6 6 0.5 Present Good 3 Good Example 1 Comparative 90 65 1.0 0.46 0.5 Present Good 1 Good Example 2

Table 3 illustrates evaluation results of the cartridges of ReferenceExamples 1 to 26 and Comparative Examples 3 to 5.

TABLE 3 Presence or absence of Judgment of amount storage area oftension of change in tape adjustment information width (2) ReferenceExample 1 Absent 4 Reference Example 2 Absent 5 Reference Example 3Absent 6 Reference Example 4 Absent 7 Reference Example 5 Absent 7Reference Example 6 Absent 8 Reference Example 7 Absent 7 ReferenceExample 8 Absent 7 Reference Example 9 Absent 8 Reference Example 10Absent 8 Reference Example 11 Absent 8 Reference Example 12 Absent 7Reference Example 13 Absent 7 Reference Example 14 Absent 7 ReferenceExample 15 Absent 7 Reference Example 16 Absent 7 Reference Example 17Absent 7 Reference Example 18 Absent 7 Reference Example 19 Absent 7Reference Example 20 Absent 7 Reference Example 21 Absent 7 ReferenceExample 22 Absent 8 Reference Example 23 Absent 8 Reference Example 24Absent 8 Reference Example 25 Absent 7 Reference Example 26 Absent 4Comparative Example 3 Absent 1 Comparative Example 4 Absent 1Comparative Example 5 Absent 1 Note that the symbols in Tables 1 and 2mean the following measured values. T_(sub): average thickness ofsubstrate t_(T): thickness of magnetic tape Δw: dimensional changeamount of magnetic tape in width direction thereof with respect totension change of the magnetic tape in longitudinal direction thereof α:temperature expansion coefficient of magnetic tape β: humidity expansioncoefficient of magnetic tape ρ: Poisson's ratio of magnetic tape σ_(MD):elastic limit value of magnetic tape in longitudinal direction thereofV: tensile rate in elastic limit measurement t_(m): average thickness ofrecording layer R2: squareness ratio of magnetic tape in thicknessdirection (perpendicular direction) thereof t_(u): average thickness ofbase layer t_(b): average thickness of back layer R_(b): surfaceroughness of back layer μ: interlayer friction coefficient betweenmagnetic surface and back surface

Tables 1 to 4 indicate the following.

From comparison of the evaluation results of Examples 1 to 3, 26, and 27and Comparative Examples 1, 2, and the like, it is found that adeviation from an ideal of the “effective amount of change in tapewidth” can be suppressed by setting the dimensional change amount Δw ofa magnetic tape to 650 [ppm/N]≤Δw and adjusting a tension applied to themagnetic tape in a longitudinal direction thereof using tensionadjustment information stored in a cartridge memory at the time of datarecording.

From comparison of the evaluation results of Examples 1 to 3, 26, and27, Comparative Examples 1 and 2, Reference Examples 1 to 3 and 26, andComparative Examples 3 to 5 and the like, the following is found. Inother words, by adjusting a tension applied to a magnetic tape in alongitudinal direction thereof using tension adjustment informationstored in a cartridge memory at the time of data recording, a lowerlimit value of the dimensional change amount Δw required for suppressinga deviation from an ideal of the “effective amount of change in tapewidth” can be reduced from 670 [ppm/N] to 650 [ppm/N]≤Δw.

From comparison of the evaluation results of Examples 1 to 3, 26, and 27and Comparative Examples 1, 2, and the like, it is found that thedimensional change amount Δw satisfies preferably 670 [ppm/N]≤Δw, morepreferably 680 [ppm/N]≤Δw, still more preferably 700 [ppm/N]≤Δw,particularly preferably 750 [ppm/N]≤Δw, most preferably 800 [ppm/N]≤Δwfrom a viewpoint of suppressing a deviation from an ideal of the“effective amount of change in tape width”.

From comparison of the evaluation results of Reference Examples 3 to 5and the like, it is found that the temperature expansion coefficient αpreferably satisfies 6 [ppm/° C.]≤α≤8 [ppm/° C.] from a viewpoint ofsuppressing a deviation from an ideal of the “effective amount of changein tape width”.

From comparison of the evaluation results of Reference Examples 3, 4, 6,and the like, it is found that the humidity expansion coefficient βpreferably satisfies β≤5 [ppm/% RH] from a viewpoint of suppressing adeviation from an ideal of the “effective amount of change in tapewidth”.

From comparison of the evaluation results of Reference Examples 6 to 8and the like, it is found that the Poisson's ratio preferably satisfies0.3≤ρ from a viewpoint of suppressing a deviation from an ideal of the“effective amount of change in tape width”.

From comparison of the evaluation results of Reference Examples 7, 9,10, 24, and the like, it is found that the elastic limit value amppreferably satisfies 0.8 [N]≤σ_(MD) from a viewpoint of suppressing adeviation from an ideal of the “effective amount of change in tapewidth”.

It is found that the elastic limit values σ_(MD) of Examples 9, 11, andthe like do not depend on the tensile rate V in elastic limitmeasurement.

Note that in each of Examples 1 to 27, regardless of the values of thetemperature expansion coefficient α, the humidity expansion coefficientβ, the Poisson's ratio ρ, and the elastic limit value σ_(MD) in alongitudinal direction, the result of “judgment of amount of change intape width (1)” was “8”. This is because the judgment of the amount ofchange in tape width was evaluated with eight ratings. In a case wheremore detailed evaluation (for example, evaluation with 10 ratings) ismade, it is presumed that also in Examples 1 to 27, an evaluation resultcapable of further suppressing a deviation from an ideal of the“effective amount of change in tape width” will be obtained withinnumerical ranges of the temperature expansion coefficient α, thehumidity expansion coefficient β, the Poisson's ratio ρ, and the elasticlimit value σ_(MD) in a longitudinal direction, similar to those inReference Examples 1 to 26.

From comparison of the evaluation results of Examples 9, 12, 18, and thelike, it is found that the average thickness t_(m) of the recordinglayer preferably satisfies t_(m)≤90 [nm] from a viewpoint of improvingelectromagnetic conversion characteristics.

From comparison of the evaluation results of Examples 7, 15, 19, and thelike, it is found that the surface roughness R_(b) of the back layerpreferably satisfies R_(b)≤6.0 [nm] from a viewpoint of improvingelectromagnetic conversion characteristics.

From comparison of the evaluation results of Examples 7, 16, 17, 21, andthe like, it is found that the interlayer friction coefficient μ betweenthe magnetic surface and the back surface preferably satisfies0.20≤μ≤0.80 from a viewpoint of suppressing a winding deviation.

From comparison of the evaluation results of Examples 7, 22, 23, and thelike, it is found that the squareness ratio S2 of the magnetic tape in aperpendicular direction thereof is preferably 80% or more from aviewpoint of improving electromagnetic conversion characteristics.

From comparison of the evaluation results of Example 7, 25, 26, and thelike, it is found that evaluation results similar to those in the caseof using ε iron oxide nanoparticles as the magnetic particles can beobtained by adjusting parameters such as the dimensional change amountΔw, the temperature expansion coefficient α, and the humidity expansioncoefficient β even in a case of using barium ferrite nanoparticles asthe magnetic particles.

Hereinabove, the embodiments and of the present disclosure andModifications thereof have been described specifically. However, thepresent disclosure is not limited to the above-described embodiments andExamples, but various modifications based on the technical idea of thepresent disclosure can be made.

For example, the configurations, the methods, the steps, the shapes, thematerials, the numerical values, and the like exemplified in theabove-described embodiments and Modifications are only examples, and aconfiguration, a method, a step, a shape, a material, a numerical value,and the like different therefrom may be used as necessary. Furthermore,the chemical formulas of the compounds and the like are representativeand are not limited to the described valences and the like as long asthe compounds have common names of the same compound.

Furthermore, the configurations, the methods, the steps, the shapes, thematerials, the numerical values, and the like in the above-describedembodiments and Modifications can be combined to each other as long asnot departing from the gist of the present disclosure.

Furthermore, within the numerical range described step by step here, anupper limit value or a lower limit value of a numerical range in onestage may be replaced with an upper limit value or a lower limit valueof a numerical range in another stage. The materials exemplified herecan be used singly or in combination of two or more thereof unlessotherwise specified.

Furthermore, the present disclosure can adopt the followingconfigurations.

(1)

A cartridge including:

a tape-shaped magnetic recording medium;

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in which the information includes adjustmentinformation for adjusting a tension applied to the magnetic recordingmedium in a longitudinal direction thereof,the magnetic recording medium has an average thickness t_(T) satisfyingt_(T)≤5.5 [μm], and the magnetic recording medium has a dimensionalchange amount Δw satisfying 650 [ppm/N]≤Δw in a width direction thereofwith respect to a tension change of the magnetic recording medium in thelongitudinal direction thereof.(2)

The cartridge according to (1), in which the dimensional change amountΔw satisfies 700 [ppm/N]≤Δw.

(3)

The cartridge according to (1), in which the dimensional change amountΔw satisfies 750 [ppm/N]≤Δw.

(4)

The cartridge according to (1), in which the dimensional change amountΔw satisfies 800 [ppm/N]≤Δw.

(5)

The cartridge according to any one of (1) to (4), in which theadjustment information is acquired at the time of data recording on themagnetic recording medium.

(6)

The cartridge according to (5), in which the adjustment informationincludes width-related information related to the width of the magneticrecording medium.

(7)

The cartridge according to (6), in which the width-related informationis distance information between adjacent servo tracks or widthinformation of the magnetic recording medium.

(8)

The cartridge according to any one of (5) to (7), in which theadjustment information includes environmental information around themagnetic recording medium.

(9)

The cartridge according to (8), in which the environmental informationincludes temperature information around the magnetic recording medium.

(10)

The cartridge according to (8) or (9), in which the environmentalinformation includes humidity information around the magnetic recordingmedium.

(11)

The cartridge according to any one of (5) to (10), in which theadjustment information includes tension information of the magneticrecording medium.

(12)

The cartridge according to any one of (1) to (11), in which the storageunit has:

a first storage area for storing first information conforming to amagnetic tape standard; and

a second storage area for storing second information other than thefirst information, and the second information includes the adjustmentinformation.

(13)

The cartridge according to any one of (1) to (12), in which the magneticrecording medium has a temperature expansion coefficient α satisfying 6[ppm/° C.]≤α≤8 [ppm/° C.].

(14)

The cartridge according to any one of (1) to (13), in which the magneticrecording medium has a humidity expansion coefficient β satisfying β≤5[ppm/% RH].

(15)

The cartridge according to any one of (1) to (14), in which the magneticrecording medium has a Poisson's ratio ρ satisfying 0.3≤ρ.

(16)

The cartridge according to any one of (1) to (15), in which the magneticrecording medium has an elastic limit value σ_(MD) satisfying 0.8[N]≤σ_(MD) in a longitudinal direction thereof.

(17)

The cartridge according to any one of (1) to (16), in which the magneticrecording medium can form 6000 or more data tracks.

(18)

The cartridge according to any one of (1) to (17), conforming to LTO 9or later standards.

(19)

The cartridge according to any one of (1) to (18), in which

the magnetic recording medium includes a recording layer, and

the recording layer has an average thickness t_(m) satisfying 9[nm]≤t_(m)≤90 [nm].

(20)

The cartridge according to (19), in which the average thickness t_(m) ofthe recording layer satisfies 35 [nm]≤t_(m)≤90 [nm].

(21)

The cartridge according to any one of (1) to (20), including a backlayer, in which the back layer has an average thickness t_(b) satisfyingt_(b)≤0.6 [μm].

(22)

The cartridge according to any one of (1) to (21), including a backlayer, in which the back layer has a surface roughness R_(b) satisfyingR_(b)≤6.0 [nm].

(23)

The cartridge according to any one of (1) to (22), including a magneticsurface and a back surface opposite to the magnetic surface, in which aninterlayer friction coefficient μ between the magnetic surface and theback surface satisfies 0.20≤μ≤0.80.

(24)

The cartridge according to any one of (1) to (23), in which

the magnetic recording medium includes a recording layer containingmagnetic powder, and

the magnetic powder contains ε iron oxide, hexagonal ferrite, orCo-containing spinel ferrite.

(25)

The cartridge according to any one of (1) to (24), in which the magneticrecording medium has a squareness ratio of 65% or more in aperpendicular direction thereof.

(26)

The cartridge according to any one of (1) to (25), in which the magneticrecording medium has a squareness ratio of 70% or more in aperpendicular direction thereof (27)

The cartridge according to any one of (1) to (26), in which a coerciveforce Hc1 of the magnetic recording medium in a perpendicular directionthereof and a coercive force Hc2 of the magnetic recording medium in alongitudinal direction thereof satisfy a relationship of Hc2/Hc1≤0.8.

(28)

The cartridge according to any one of (1) to (27), in which the magneticrecording medium includes a magnetic layer containing a lubricant, themagnetic layer has a surface having a large number of holes formedthereon, and the entire magnetic recording medium has a BET specificsurface area of 3.5 m²/mg or more in a state where the lubricant hasbeen removed.

(29)

A cartridge including:

a tape-shaped magnetic recording medium; and

a storage unit having an area in which adjustment information foradjusting a tension applied to the magnetic recording medium in alongitudinal direction thereof is written, in which the magneticrecording medium has an average thickness t_(T) satisfying t_(T)≤5.5[μm], and the magnetic recording medium has a dimensional change amountΔw satisfying 650 [ppm/N]≤Δw in a width direction thereof with respectto a tension change of the magnetic recording medium in the longitudinaldirection thereof.(30)

A cartridge memory used for a tape-shaped magnetic recording medium,including:

a communication unit that communicates with a recording/reproducingdevice;

a storage unit; and

a control unit that stores information received from therecording/reproducing device through the communication unit in thestorage unit, reads the information from the storage unit according to arequest from the recording/reproducing device, and transmits theinformation to the recording/reproducing device through thecommunication unit, in which the information includes adjustmentinformation for adjusting a tension applied to the magnetic recordingmedium in a longitudinal direction thereof.(31)

A cartridge memory used for a tape-shaped magnetic recording medium,including

a storage unit having an area in which adjustment information foradjusting a tension applied to the magnetic recording medium in alongitudinal direction thereof is written.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

REFERENCE SIGNS LIST

-   10 Cartridge-   11 Cartridge memory-   31 Antenna coil-   32 Rectification/power supply circuit-   33 Clock circuit-   34 Detection/modulation circuit-   35 Controller-   36 Memory-   36A First storage area-   36B Second storage area-   41 Substrate-   42 Base layer-   43 Recording layer-   44 Back layer-   50, 50A Recording/reproducing device-   51 Spindle-   52 Reel-   53 Spindle drive device-   54 Reel drive device-   55 Guide roller-   56 Head unit-   57 Reader/writer-   58 Communication interface-   59 Control device-   60 Thermometer-   61 Hygrometer-   100, 100A Recording/reproducing system-   MT Magnetic tape

The invention claimed is:
 1. A cartridge comprising: a tape-shapedmagnetic recording medium having a magnetic layer, a non-magnetic layer,a base layer and a back layer; and a cartridge memory, wherein thecartridge memory comprises: a communication unit that communicates witha recording/reproducing device in a state where the cartridge is loadedon the recording/reproducing device; a storage unit that stores aninformation; and a control unit that reads the information from thestorage unit according to a request from the recording/reproducingdevice, and transmits the information to the recording/reproducingdevice through the communication unit, wherein the information includesa width-related information related to a width of the tape-shapedrecording medium, and wherein a plurality of servo bands are providedalong a longitudinal direction of the tape-shaped magnetic recordingmedium in the magnetic layer, a thickness of the tape-shaped magneticrecording medium is equal to or less than 5.5 μm, and a dimensionalchange amount Δw in a width direction of the tape-shaped magneticrecording medium with respect to a tension change in the longitudinaldirection of the tape-shaped magnetic recording medium is 650ppm/N≤Δw≤8000 ppm, wherein the dimensional change amount Δw isdetermined according to:${\Delta{w\lbrack {{ppm}/N} \rbrack}} = {\frac{{{D( {0.2N} )}\lbrack{mm}\rbrack} - {{D( {1.N} )}\lbrack{mm}\rbrack}}{{D( {0.2N} )}\lbrack{mm}\rbrack} \times \frac{1,000,000}{( {1.\lbrack N\rbrack} ) - ( {0.2\lbrack N\rbrack} )}}$wherein D(0.2N) and D(1.0N) represent widths of a sample of thetape-shaped magnetic recording medium subject to loads of 0.2N and 1.0N,respectively, in the longitudinal direction of the tape-shaped magneticrecording medium under 25° C. and 50% RH, and a width of the sample ofthe tape-shaped magnetic recording medium is ½ inch prior to beingsubject to a load.
 2. The cartridge according to claim 1, wherein thedimensional change amount Δw satisfies 670 ppm/N≤Δw≤8000 ppm.
 3. Thecartridge according to claim 1, wherein the dimensional change amount Δwsatisfies 680 ppm/N≤Δw≤8000 ppm.
 4. The cartridge according to claim 1,wherein the dimensional change amount Δw satisfies 700 ppm/N≤Δw≤8000ppm.
 5. The cartridge according to claim 1, wherein the thickness of thetape-shaped magnetic recording medium is equal to or less than 5.2 μm.6. The cartridge according to claim 1, wherein the storage unit has: afirst storage area for storing first information conforming to amagnetic tape standard; and a second storage area for storing secondinformation other than the first information, the first informationincludes the manufacturing information of the cartridge and the secondinformation includes the adjustment information.
 7. The cartridgeaccording to claim 6, wherein the storage unit has a plurality of banks,wherein the first storage area of the storage unit includes a firstgroup of the plurality of banks, and wherein the second storage area ofthe storage unit includes a second group of the plurality of banks. 8.The cartridge according to claim 1, wherein a temperature expansioncoefficient α of the tape-shaped magnetic recording medium satisfies 6ppm/° C.≤α≤8 ppm/° C.
 9. The cartridge according to claim 1, furthercomprising a rectification/power supply circuit.
 10. The cartridgeaccording to claim 1, further comprising a clock circuit.
 11. Thecartridge according to claim 1, further comprising adetection/modulation circuit.
 12. The cartridge according to claim 1,wherein the storage unit includes a non-volatile memory.
 13. Thecartridge according to claim 1, wherein a humidity expansion coefficientβ of the tape-shaped magnetic recording medium satisfies β≤5 ppm/% RH.14. The cartridge according to claim 1, wherein a Poisson's ratio ρ ofthe tape-shaped magnetic recording medium satisfies 0.3≤ρ.
 15. Thecartridge according to claim 1, wherein an elastic limit value σ_(MD) ina longitudinal direction satisfies 0.8 N≤σ_(MD).
 16. The cartridgeaccording to claim 15, wherein the elastic limit value σ_(MD) does notdepend on a rate V in elastic limit measurement.
 17. The cartridgeaccording to claim 1, wherein the storage unit has a storage capacity of32 KB or more.
 18. The cartridge according to claim 1, wherein thecommunication unit has an antenna coil.
 19. The cartridge according toclaim 1, wherein a servo signal is written in the plurality of servobands.
 20. The cartridge according to claim 19, wherein the servo signalis a V-shaped servo pattern.
 21. The cartridge according to claim 1,wherein a number of the servo bands is 5 or more.
 22. The cartridgeaccording to claim 1, wherein a number of the servo bands is 9 or more.23. The cartridge according to claim 1, wherein a servo bandwidth of aservo band of the plurality of servo bands is 10 μm or more, and 95 μmor less.
 24. The cartridge according to claim 1, wherein a servobandwidth of a servo band of the plurality of servo bands is 10 μm ormore, and 60 μm or less.
 25. The cartridge according to claim 1, whereinthe cartridge memory faces a reader/writer of the recording/reproducingdevice in the state where the cartridge is loaded on therecording/reproducing device.
 26. The cartridge according to claim 1,wherein the back layer has an average thickness t_(b) satisfyingt_(b)≤0.6 μm.
 27. The cartridge according to claim 1, wherein thecartridge memory faces a reader/writer of the recording/reproducingdevice in the state where the cartridge is loaded on therecording/reproducing device; the storage unit has: a first storage areafor storing first information conforming to a magnetic tape standard;and a second storage area for storing second information other than thefirst information; the first information includes the manufacturinginformation of the cartridge; the second information includes theadjustment information; the adjustment information includes at least oneof distance information between adjacent servo bands of the plurality ofservo bands or the width-related information of the tape-shaped magneticrecording medium.